CVE-2021-47245 (GCVE-0-2021-47245)
Vulnerability from cvelistv5 – Published: 2024-05-21 14:19 – Updated: 2026-08-05 08:46
VLAI
EPSS
VEX
Title
netfilter: synproxy: Fix out of bounds when parsing TCP options
Summary
In the Linux kernel, the following vulnerability has been resolved:
netfilter: synproxy: Fix out of bounds when parsing TCP options
The TCP option parser in synproxy (synproxy_parse_options) could read
one byte out of bounds. When the length is 1, the execution flow gets
into the loop, reads one byte of the opcode, and if the opcode is
neither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds
the length of 1.
This fix is inspired by commit 9609dad263f8 ("ipv4: tcp_input: fix stack
out of bounds when parsing TCP options.").
v2 changes:
Added an early return when length < 0 to avoid calling
skb_header_pointer with negative length.
Severity
8.2 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-05-23 18:09 UTC
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | |
|---|---|---|---|
| Linux | Linux |
Affected:
48b1de4c110a7afa4b85862f6c75af817db26fad , < e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8
(git)
Affected: 48b1de4c110a7afa4b85862f6c75af817db26fad , < 576c1526b4d83c44ad7b673cb841f36cbc6cb6c4 (git) Affected: 48b1de4c110a7afa4b85862f6c75af817db26fad , < 674b5f0c6a4fc5d3abce877048290cea6091fcb1 (git) Affected: 48b1de4c110a7afa4b85862f6c75af817db26fad , < 7d9a9a1a88a3da574e019b4de756bc73337b3b0b (git) Affected: 48b1de4c110a7afa4b85862f6c75af817db26fad , < 6defc77d48eff74075b80ad5925061b2fc010d98 (git) Affected: 48b1de4c110a7afa4b85862f6c75af817db26fad , < 9cdf299ba4e153b5e56187648420de22c6216f02 (git) Affected: 48b1de4c110a7afa4b85862f6c75af817db26fad , < f648089337cb8ed40b2bb96e244f72b9d97dc96b (git) Affected: 48b1de4c110a7afa4b85862f6c75af817db26fad , < 5fc177ab759418c9537433e63301096e733fb915 (git) |
|
| Linux | Linux |
Affected:
3.12
Unaffected: 0 , < 3.12 (semver) Unaffected: 4.4.274 , ≤ 4.4.* (semver) Unaffected: 4.9.274 , ≤ 4.9.* (semver) Unaffected: 4.14.238 , ≤ 4.14.* (semver) Unaffected: 4.19.196 , ≤ 4.19.* (semver) Unaffected: 5.4.128 , ≤ 5.4.* (semver) Unaffected: 5.10.46 , ≤ 5.10.* (semver) Unaffected: 5.12.13 , ≤ 5.12.* (semver) Unaffected: 5.13 , ≤ * (original_commit_for_fix) |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2021-47245",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2024-05-23T18:09:52.562711Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2024-06-04T17:13:37.955Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
},
{
"providerMetadata": {
"dateUpdated": "2024-08-04T05:32:07.394Z",
"orgId": "af854a3a-2127-422b-91ae-364da2661108",
"shortName": "CVE"
},
"references": [
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/576c1526b4d83c44ad7b673cb841f36cbc6cb6c4"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/674b5f0c6a4fc5d3abce877048290cea6091fcb1"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/7d9a9a1a88a3da574e019b4de756bc73337b3b0b"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/6defc77d48eff74075b80ad5925061b2fc010d98"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/9cdf299ba4e153b5e56187648420de22c6216f02"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/f648089337cb8ed40b2bb96e244f72b9d97dc96b"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/5fc177ab759418c9537433e63301096e733fb915"
}
],
"title": "CVE Program Container"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/netfilter/nf_synproxy_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "576c1526b4d83c44ad7b673cb841f36cbc6cb6c4",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "674b5f0c6a4fc5d3abce877048290cea6091fcb1",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "7d9a9a1a88a3da574e019b4de756bc73337b3b0b",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "6defc77d48eff74075b80ad5925061b2fc010d98",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "9cdf299ba4e153b5e56187648420de22c6216f02",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "f648089337cb8ed40b2bb96e244f72b9d97dc96b",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "5fc177ab759418c9537433e63301096e733fb915",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/netfilter/nf_synproxy_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "3.12"
},
{
"lessThan": "3.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.4.*",
"status": "unaffected",
"version": "4.4.274",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.9.*",
"status": "unaffected",
"version": "4.9.274",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.14.*",
"status": "unaffected",
"version": "4.14.238",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.19.*",
"status": "unaffected",
"version": "4.19.196",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.4.*",
"status": "unaffected",
"version": "5.4.128",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.46",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.12.*",
"status": "unaffected",
"version": "5.12.13",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "5.13",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.4.274",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.9.274",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.14.238",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.19.196",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.4.128",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.46",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.12.13",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.13",
"versionStartIncluding": "3.12",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: synproxy: Fix out of bounds when parsing TCP options\n\nThe TCP option parser in synproxy (synproxy_parse_options) could read\none byte out of bounds. When the length is 1, the execution flow gets\ninto the loop, reads one byte of the opcode, and if the opcode is\nneither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds\nthe length of 1.\n\nThis fix is inspired by commit 9609dad263f8 (\"ipv4: tcp_input: fix stack\nout of bounds when parsing TCP options.\").\n\nv2 changes:\n\nAdded an early return when length \u003c 0 to avoid calling\nskb_header_pointer with negative length."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.2,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - synproxy_parse_options runs on received TCP packets in ipt_SYNPROXY/nft_synproxy and ipv4/ipv6_synproxy_hook; SYNPROXY is deployed on internet-facing hosts to mitigate SYN floods, so a remote peer triggers it with crafted TCP options.\nAC:L - The attacker fully controls the TCP option bytes and can reliably produce length==1 (e.g., NOPs plus a non-EOL/NOP kind) so the parser reads one byte past the end of the option data; no race or external condition is required.\nPR:N - Exploitation needs only the ability to send TCP segments to a host where SYNPROXY is enabled; no authentication or local account is required on that network path.\nUI:N - The vulnerable parser runs automatically on matching inbound TCP packets; no victim user action is required.\nS:U - Impact stays within the same kernel/host security authority; there is no VM, IOMMU, or other cross-boundary escape.\nC:L - The bug is a strictly one-byte out-of-bounds read (stack buf[40] or past copied option bytes) into a local opsize; per guidance that is a limited/bounded read (C:L), not an arbitrary read primitive.\nI:N - This is a read-only OOB; the byte is only used for length checks and is not written to attacker-controlled state, so there is no integrity or write primitive.\nA:H - Out-of-bounds kernel memory access can fault or otherwise disrupt the host (and is treated as DoS by multiple vendors); when uncertain, availability is scored High."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T08:46:56.392Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8"
},
{
"url": "https://git.kernel.org/stable/c/576c1526b4d83c44ad7b673cb841f36cbc6cb6c4"
},
{
"url": "https://git.kernel.org/stable/c/674b5f0c6a4fc5d3abce877048290cea6091fcb1"
},
{
"url": "https://git.kernel.org/stable/c/7d9a9a1a88a3da574e019b4de756bc73337b3b0b"
},
{
"url": "https://git.kernel.org/stable/c/6defc77d48eff74075b80ad5925061b2fc010d98"
},
{
"url": "https://git.kernel.org/stable/c/9cdf299ba4e153b5e56187648420de22c6216f02"
},
{
"url": "https://git.kernel.org/stable/c/f648089337cb8ed40b2bb96e244f72b9d97dc96b"
},
{
"url": "https://git.kernel.org/stable/c/5fc177ab759418c9537433e63301096e733fb915"
}
],
"title": "netfilter: synproxy: Fix out of bounds when parsing TCP options",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2021-47245",
"datePublished": "2024-05-21T14:19:43.648Z",
"dateReserved": "2024-04-10T18:59:19.533Z",
"dateUpdated": "2026-08-05T08:46:56.392Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2021-47245",
"date": "2026-10-03",
"epss": "0.00784",
"percentile": "0.54505"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/netfilter/nf_synproxy_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "576c1526b4d83c44ad7b673cb841f36cbc6cb6c4",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "674b5f0c6a4fc5d3abce877048290cea6091fcb1",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "7d9a9a1a88a3da574e019b4de756bc73337b3b0b",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "6defc77d48eff74075b80ad5925061b2fc010d98",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "9cdf299ba4e153b5e56187648420de22c6216f02",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "f648089337cb8ed40b2bb96e244f72b9d97dc96b",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "5fc177ab759418c9537433e63301096e733fb915",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/netfilter/nf_synproxy_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "3.12"
},
{
"lessThan": "3.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.4.*",
"status": "unaffected",
"version": "4.4.274",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.9.*",
"status": "unaffected",
"version": "4.9.274",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.14.*",
"status": "unaffected",
"version": "4.14.238",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.19.*",
"status": "unaffected",
"version": "4.19.196",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.4.*",
"status": "unaffected",
"version": "5.4.128",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.46",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.12.*",
"status": "unaffected",
"version": "5.12.13",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "5.13",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "0DCDAEC4-D25F-4160-B3C9-A7E204F7DA2A",
"versionEndExcluding": "4.4.274",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "0A84D5BC-006F-41C5-A54D-6D45236009B3",
"versionEndExcluding": "4.9.274",
"versionStartIncluding": "4.5",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "C3C0DBBF-0923-4D2A-9178-134691F9933F",
"versionEndExcluding": "4.14.238",
"versionStartIncluding": "4.10",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "F3CAB837-7D38-4934-AD4F-195CEFD754E6",
"versionEndExcluding": "4.19.196",
"versionStartIncluding": "4.15",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "6267BD4E-BE25-48B5-B850-4B493440DAFA",
"versionEndExcluding": "5.4.128",
"versionStartIncluding": "4.20",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "59455D13-A902-42E1-97F7-5ED579777193",
"versionEndExcluding": "5.10.46",
"versionStartIncluding": "5.5",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "7806E7E5-6D4F-4E18-81C1-79B3C60EE855",
"versionEndExcluding": "5.12.13",
"versionStartIncluding": "5.11",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:*",
"matchCriteriaId": "0CBAD0FC-C281-4666-AB2F-F8E6E1165DF7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc2:*:*:*:*:*:*",
"matchCriteriaId": "96AC23B2-D46A-49D9-8203-8E1BEDCA8532",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc3:*:*:*:*:*:*",
"matchCriteriaId": "DA610E30-717C-4700-9F77-A3C9244F3BFD",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc4:*:*:*:*:*:*",
"matchCriteriaId": "1ECD33F5-85BE-430B-8F86-8D7BD560311D",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc5:*:*:*:*:*:*",
"matchCriteriaId": "CF351855-2437-4CF5-AD7C-BDFA51F27683",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc6:*:*:*:*:*:*",
"matchCriteriaId": "25A855BA-2118-44F2-90EF-EBBB12AF51EF",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: synproxy: Fix out of bounds when parsing TCP options\n\nThe TCP option parser in synproxy (synproxy_parse_options) could read\none byte out of bounds. When the length is 1, the execution flow gets\ninto the loop, reads one byte of the opcode, and if the opcode is\nneither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds\nthe length of 1.\n\nThis fix is inspired by commit 9609dad263f8 (\"ipv4: tcp_input: fix stack\nout of bounds when parsing TCP options.\").\n\nv2 changes:\n\nAdded an early return when length \u003c 0 to avoid calling\nskb_header_pointer with negative length."
},
{
"lang": "es",
"value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: netfilter: synproxy: correcci\u00f3n de l\u00edmites al analizar opciones TCP. El analizador de opciones TCP en synproxy (synproxy_parse_options) podr\u00eda leer un byte fuera de los l\u00edmites. Cuando la longitud es 1, el flujo de ejecuci\u00f3n entra en el bucle, lee un byte del c\u00f3digo de operaci\u00f3n y, si el c\u00f3digo de operaci\u00f3n no es TCPOPT_EOL ni TCPOPT_NOP, lee un byte m\u00e1s, que excede la longitud de 1. Esta soluci\u00f3n est\u00e1 inspirada en la confirmaci\u00f3n. 9609dad263f8 (\"ipv4: tcp_input: corrige la pila fuera de los l\u00edmites al analizar las opciones de TCP\"). Cambios en v2: se agreg\u00f3 un retorno anticipado cuando la longitud \u0026lt;0 para evitar llamar a skb_header_pointer con una longitud negativa."
}
],
"id": "CVE-2021-47245",
"lastModified": "2026-08-04T10:16:54.730",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 8.2,
"baseSeverity": "HIGH",
"confidentialityImpact": "LOW",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 4.2,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
},
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.1,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.2,
"source": "nvd@nist.gov",
"type": "Primary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2021-47245",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2024-05-23T18:09:52.562711Z",
"version": "2.0.3"
}
}
]
},
"published": "2024-05-21T15:15:13.550",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/576c1526b4d83c44ad7b673cb841f36cbc6cb6c4"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/5fc177ab759418c9537433e63301096e733fb915"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/674b5f0c6a4fc5d3abce877048290cea6091fcb1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/6defc77d48eff74075b80ad5925061b2fc010d98"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/7d9a9a1a88a3da574e019b4de756bc73337b3b0b"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/9cdf299ba4e153b5e56187648420de22c6216f02"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/f648089337cb8ed40b2bb96e244f72b9d97dc96b"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/576c1526b4d83c44ad7b673cb841f36cbc6cb6c4"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/5fc177ab759418c9537433e63301096e733fb915"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/674b5f0c6a4fc5d3abce877048290cea6091fcb1"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/6defc77d48eff74075b80ad5925061b2fc010d98"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/7d9a9a1a88a3da574e019b4de756bc73337b3b0b"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/9cdf299ba4e153b5e56187648420de22c6216f02"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/f648089337cb8ed40b2bb96e244f72b9d97dc96b"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-125"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-08-04T20:00:02+00:00",
"cve": "CVE-2021-47245",
"id": "CVE-2021-47245",
"initial_release_date": "2021-01-01T00:00:00+00:00",
"product_status:known_affected": "42",
"product_status:known_not_affected": "156",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: netfilter: synproxy: Fix out of bounds when parsing TCP options",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47245.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"providerMetadata": {
"dateUpdated": "2024-08-04T05:32:07.394Z",
"orgId": "af854a3a-2127-422b-91ae-364da2661108",
"shortName": "CVE"
},
"references": [
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/576c1526b4d83c44ad7b673cb841f36cbc6cb6c4"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/674b5f0c6a4fc5d3abce877048290cea6091fcb1"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/7d9a9a1a88a3da574e019b4de756bc73337b3b0b"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/6defc77d48eff74075b80ad5925061b2fc010d98"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/9cdf299ba4e153b5e56187648420de22c6216f02"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/f648089337cb8ed40b2bb96e244f72b9d97dc96b"
},
{
"tags": [
"x_transferred"
],
"url": "https://git.kernel.org/stable/c/5fc177ab759418c9537433e63301096e733fb915"
}
],
"title": "CVE Program Container"
},
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2021-47245",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2024-05-23T18:09:52.562711Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2024-05-23T18:09:57.179Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/netfilter/nf_synproxy_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "576c1526b4d83c44ad7b673cb841f36cbc6cb6c4",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "674b5f0c6a4fc5d3abce877048290cea6091fcb1",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "7d9a9a1a88a3da574e019b4de756bc73337b3b0b",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "6defc77d48eff74075b80ad5925061b2fc010d98",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "9cdf299ba4e153b5e56187648420de22c6216f02",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "f648089337cb8ed40b2bb96e244f72b9d97dc96b",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
},
{
"lessThan": "5fc177ab759418c9537433e63301096e733fb915",
"status": "affected",
"version": "48b1de4c110a7afa4b85862f6c75af817db26fad",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/netfilter/nf_synproxy_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "3.12"
},
{
"lessThan": "3.12",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.4.*",
"status": "unaffected",
"version": "4.4.274",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.9.*",
"status": "unaffected",
"version": "4.9.274",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.14.*",
"status": "unaffected",
"version": "4.14.238",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.19.*",
"status": "unaffected",
"version": "4.19.196",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.4.*",
"status": "unaffected",
"version": "5.4.128",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.46",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.12.*",
"status": "unaffected",
"version": "5.12.13",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "5.13",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.4.274",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.9.274",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.14.238",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.19.196",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.4.128",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.46",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.12.13",
"versionStartIncluding": "3.12",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.13",
"versionStartIncluding": "3.12",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: synproxy: Fix out of bounds when parsing TCP options\n\nThe TCP option parser in synproxy (synproxy_parse_options) could read\none byte out of bounds. When the length is 1, the execution flow gets\ninto the loop, reads one byte of the opcode, and if the opcode is\nneither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds\nthe length of 1.\n\nThis fix is inspired by commit 9609dad263f8 (\"ipv4: tcp_input: fix stack\nout of bounds when parsing TCP options.\").\n\nv2 changes:\n\nAdded an early return when length \u003c 0 to avoid calling\nskb_header_pointer with negative length."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.2,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - synproxy_parse_options runs on received TCP packets in ipt_SYNPROXY/nft_synproxy and ipv4/ipv6_synproxy_hook; SYNPROXY is deployed on internet-facing hosts to mitigate SYN floods, so a remote peer triggers it with crafted TCP options.\nAC:L - The attacker fully controls the TCP option bytes and can reliably produce length==1 (e.g., NOPs plus a non-EOL/NOP kind) so the parser reads one byte past the end of the option data; no race or external condition is required.\nPR:N - Exploitation needs only the ability to send TCP segments to a host where SYNPROXY is enabled; no authentication or local account is required on that network path.\nUI:N - The vulnerable parser runs automatically on matching inbound TCP packets; no victim user action is required.\nS:U - Impact stays within the same kernel/host security authority; there is no VM, IOMMU, or other cross-boundary escape.\nC:L - The bug is a strictly one-byte out-of-bounds read (stack buf[40] or past copied option bytes) into a local opsize; per guidance that is a limited/bounded read (C:L), not an arbitrary read primitive.\nI:N - This is a read-only OOB; the byte is only used for length checks and is not written to attacker-controlled state, so there is no integrity or write primitive.\nA:H - Out-of-bounds kernel memory access can fault or otherwise disrupt the host (and is treated as DoS by multiple vendors); when uncertain, availability is scored High."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T08:46:56.392Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/e1eb98cfeafdd85537e7e3cefe93ca9bfbcc3ea8"
},
{
"url": "https://git.kernel.org/stable/c/576c1526b4d83c44ad7b673cb841f36cbc6cb6c4"
},
{
"url": "https://git.kernel.org/stable/c/674b5f0c6a4fc5d3abce877048290cea6091fcb1"
},
{
"url": "https://git.kernel.org/stable/c/7d9a9a1a88a3da574e019b4de756bc73337b3b0b"
},
{
"url": "https://git.kernel.org/stable/c/6defc77d48eff74075b80ad5925061b2fc010d98"
},
{
"url": "https://git.kernel.org/stable/c/9cdf299ba4e153b5e56187648420de22c6216f02"
},
{
"url": "https://git.kernel.org/stable/c/f648089337cb8ed40b2bb96e244f72b9d97dc96b"
},
{
"url": "https://git.kernel.org/stable/c/5fc177ab759418c9537433e63301096e733fb915"
}
],
"title": "netfilter: synproxy: Fix out of bounds when parsing TCP options",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2021-47245",
"datePublished": "2024-05-21T14:19:43.648Z",
"dateReserved": "2024-04-10T18:59:19.533Z",
"dateUpdated": "2026-08-05T08:46:56.392Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…