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EUVD-2026-344536
European Vulnerability Database identifier assigned by ENISAReserved
2026-10-02 07:56
Assigner
ENISA
Alias of
a CVE record, shown under related vulnerabilities.
This identifier carries no description, severity or references of its own:
they belong to that CVE.
{
"assigner": "ENISA",
"date_reserved": "2026-10-02T07:56:46.589873+00:00",
"id": "EUVD-2026-344536"
}
CVE-2021-47656 (GCVE-0-2021-47656)
Vulnerability from cvelistv5 – Published: 2025-02-26 01:54 – Updated: 2026-08-05 08:48
VLAI
EPSS
VEX
Title
jffs2: fix use-after-free in jffs2_clear_xattr_subsystem
Summary
In the Linux kernel, the following vulnerability has been resolved:
jffs2: fix use-after-free in jffs2_clear_xattr_subsystem
When we mount a jffs2 image, assume that the first few blocks of
the image are normal and contain at least one xattr-related inode,
but the next block is abnormal. As a result, an error is returned
in jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then
called in jffs2_build_filesystem() and then again in
jffs2_do_fill_super().
Finally we can observe the following report:
==================================================================
BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac
Read of size 8 at addr ffff8881243384e0 by task mount/719
Call Trace:
dump_stack+0x115/0x16b
jffs2_clear_xattr_subsystem+0x95/0x6ac
jffs2_do_fill_super+0x84f/0xc30
jffs2_fill_super+0x2ea/0x4c0
mtd_get_sb+0x254/0x400
mtd_get_sb_by_nr+0x4f/0xd0
get_tree_mtd+0x498/0x840
jffs2_get_tree+0x25/0x30
vfs_get_tree+0x8d/0x2e0
path_mount+0x50f/0x1e50
do_mount+0x107/0x130
__se_sys_mount+0x1c5/0x2f0
__x64_sys_mount+0xc7/0x160
do_syscall_64+0x45/0x70
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Allocated by task 719:
kasan_save_stack+0x23/0x60
__kasan_kmalloc.constprop.0+0x10b/0x120
kasan_slab_alloc+0x12/0x20
kmem_cache_alloc+0x1c0/0x870
jffs2_alloc_xattr_ref+0x2f/0xa0
jffs2_scan_medium.cold+0x3713/0x4794
jffs2_do_mount_fs.cold+0xa7/0x2253
jffs2_do_fill_super+0x383/0xc30
jffs2_fill_super+0x2ea/0x4c0
[...]
Freed by task 719:
kmem_cache_free+0xcc/0x7b0
jffs2_free_xattr_ref+0x78/0x98
jffs2_clear_xattr_subsystem+0xa1/0x6ac
jffs2_do_mount_fs.cold+0x5e6/0x2253
jffs2_do_fill_super+0x383/0xc30
jffs2_fill_super+0x2ea/0x4c0
[...]
The buggy address belongs to the object at ffff8881243384b8
which belongs to the cache jffs2_xattr_ref of size 48
The buggy address is located 40 bytes inside of
48-byte region [ffff8881243384b8, ffff8881243384e8)
[...]
==================================================================
The triggering of the BUG is shown in the following stack:
-----------------------------------------------------------
jffs2_fill_super
jffs2_do_fill_super
jffs2_do_mount_fs
jffs2_build_filesystem
jffs2_scan_medium
jffs2_scan_eraseblock <--- ERROR
jffs2_clear_xattr_subsystem <--- free
jffs2_clear_xattr_subsystem <--- free again
-----------------------------------------------------------
An error is returned in jffs2_do_mount_fs(). If the error is returned
by jffs2_sum_init(), the jffs2_clear_xattr_subsystem() does not need to
be executed. If the error is returned by jffs2_build_filesystem(), the
jffs2_clear_xattr_subsystem() also does not need to be executed again.
So move jffs2_clear_xattr_subsystem() from 'out_inohash' to 'out_root'
to fix this UAF problem.
Severity
7.8 (High)
7.8 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-02-27 17:59 UTC
CWE
- CWE-416 - Use After Free
Assigner
References
9 references
Impacted products
2 products
| Vendor | Product | Version | |
|---|---|---|---|
| Linux | Linux |
Affected:
aa98d7cf59b5b0764d3502662053489585faf2fe , < 9150cb625b46f68d524f4cfd491f1aafc23e10a9
(git)
Affected: aa98d7cf59b5b0764d3502662053489585faf2fe , < 3bd2454162ec6bbb5503233c804fce6e4b6dcec5 (git) Affected: aa98d7cf59b5b0764d3502662053489585faf2fe , < c3b07c875fa8f906f932976460fd14798596f101 (git) Affected: aa98d7cf59b5b0764d3502662053489585faf2fe , < 30bf7244acf32f19cb722c39f7bc1c2a9f300422 (git) Affected: aa98d7cf59b5b0764d3502662053489585faf2fe , < 7bb7428dd73991bf4b3a7a61b493ca50046c2b13 (git) Affected: aa98d7cf59b5b0764d3502662053489585faf2fe , < 7a75740206af5f17e9f3efa384211cba70213da1 (git) Affected: aa98d7cf59b5b0764d3502662053489585faf2fe , < 22327bd7988f21de3a53c1373f3b81542bfe1f44 (git) Affected: aa98d7cf59b5b0764d3502662053489585faf2fe , < 8c0f024f29e055840a5a89fe23b96ae3f921afed (git) Affected: aa98d7cf59b5b0764d3502662053489585faf2fe , < 4c7c44ee1650677fbe89d86edbad9497b7679b5c (git) |
|
| Linux | Linux |
Affected:
2.6.18
Unaffected: 0 , < 2.6.18 (semver) Unaffected: 4.9.311 , ≤ 4.9.* (semver) Unaffected: 4.14.276 , ≤ 4.14.* (semver) Unaffected: 4.19.238 , ≤ 4.19.* (semver) Unaffected: 5.4.189 , ≤ 5.4.* (semver) Unaffected: 5.10.110 , ≤ 5.10.* (semver) Unaffected: 5.15.33 , ≤ 5.15.* (semver) Unaffected: 5.16.19 , ≤ 5.16.* (semver) Unaffected: 5.17.2 , ≤ 5.17.* (semver) Unaffected: 5.18 , ≤ * (original_commit_for_fix) |
{
"containers": {
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{
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
}
},
{
"other": {
"content": {
"id": "CVE-2021-47656",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2025-02-27T17:59:35.381270Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-416",
"description": "CWE-416 Use After Free",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2025-02-27T18:02:30.510Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/jffs2/fs.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "9150cb625b46f68d524f4cfd491f1aafc23e10a9",
"status": "affected",
"version": "aa98d7cf59b5b0764d3502662053489585faf2fe",
"versionType": "git"
},
{
"lessThan": "3bd2454162ec6bbb5503233c804fce6e4b6dcec5",
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"version": "aa98d7cf59b5b0764d3502662053489585faf2fe",
"versionType": "git"
},
{
"lessThan": "c3b07c875fa8f906f932976460fd14798596f101",
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"versionType": "git"
},
{
"lessThan": "30bf7244acf32f19cb722c39f7bc1c2a9f300422",
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"versionType": "git"
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{
"lessThan": "7bb7428dd73991bf4b3a7a61b493ca50046c2b13",
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"versionType": "git"
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{
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{
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"versionType": "git"
},
{
"lessThan": "8c0f024f29e055840a5a89fe23b96ae3f921afed",
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{
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{
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"programFiles": [
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],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.18"
},
{
"lessThan": "2.6.18",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.9.*",
"status": "unaffected",
"version": "4.9.311",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.14.*",
"status": "unaffected",
"version": "4.14.276",
"versionType": "semver"
},
{
"lessThanOrEqual": "4.19.*",
"status": "unaffected",
"version": "4.19.238",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.4.*",
"status": "unaffected",
"version": "5.4.189",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.110",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.33",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.16.*",
"status": "unaffected",
"version": "5.16.19",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.17.*",
"status": "unaffected",
"version": "5.17.2",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "5.18",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "4.9.311",
"versionStartIncluding": "2.6.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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},
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},
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"versionEndExcluding": "5.4.189",
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"vulnerable": true
},
{
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},
{
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"versionEndExcluding": "5.17.2",
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"vulnerable": true
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}
],
"negate": false,
"operator": "OR"
}
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}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\njffs2: fix use-after-free in jffs2_clear_xattr_subsystem\n\nWhen we mount a jffs2 image, assume that the first few blocks of\nthe image are normal and contain at least one xattr-related inode,\nbut the next block is abnormal. As a result, an error is returned\nin jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then\ncalled in jffs2_build_filesystem() and then again in\njffs2_do_fill_super().\n\nFinally we can observe the following report:\n ==================================================================\n BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac\n Read of size 8 at addr ffff8881243384e0 by task mount/719\n\n Call Trace:\n dump_stack+0x115/0x16b\n jffs2_clear_xattr_subsystem+0x95/0x6ac\n jffs2_do_fill_super+0x84f/0xc30\n jffs2_fill_super+0x2ea/0x4c0\n mtd_get_sb+0x254/0x400\n mtd_get_sb_by_nr+0x4f/0xd0\n get_tree_mtd+0x498/0x840\n jffs2_get_tree+0x25/0x30\n vfs_get_tree+0x8d/0x2e0\n path_mount+0x50f/0x1e50\n do_mount+0x107/0x130\n __se_sys_mount+0x1c5/0x2f0\n __x64_sys_mount+0xc7/0x160\n do_syscall_64+0x45/0x70\n entry_SYSCALL_64_after_hwframe+0x44/0xa9\n\n Allocated by task 719:\n kasan_save_stack+0x23/0x60\n __kasan_kmalloc.constprop.0+0x10b/0x120\n kasan_slab_alloc+0x12/0x20\n kmem_cache_alloc+0x1c0/0x870\n jffs2_alloc_xattr_ref+0x2f/0xa0\n jffs2_scan_medium.cold+0x3713/0x4794\n jffs2_do_mount_fs.cold+0xa7/0x2253\n jffs2_do_fill_super+0x383/0xc30\n jffs2_fill_super+0x2ea/0x4c0\n [...]\n\n Freed by task 719:\n kmem_cache_free+0xcc/0x7b0\n jffs2_free_xattr_ref+0x78/0x98\n jffs2_clear_xattr_subsystem+0xa1/0x6ac\n jffs2_do_mount_fs.cold+0x5e6/0x2253\n jffs2_do_fill_super+0x383/0xc30\n jffs2_fill_super+0x2ea/0x4c0\n [...]\n\n The buggy address belongs to the object at ffff8881243384b8\n which belongs to the cache jffs2_xattr_ref of size 48\n The buggy address is located 40 bytes inside of\n 48-byte region [ffff8881243384b8, ffff8881243384e8)\n [...]\n ==================================================================\n\nThe triggering of the BUG is shown in the following stack:\n-----------------------------------------------------------\njffs2_fill_super\n jffs2_do_fill_super\n jffs2_do_mount_fs\n jffs2_build_filesystem\n jffs2_scan_medium\n jffs2_scan_eraseblock \u003c--- ERROR\n jffs2_clear_xattr_subsystem \u003c--- free\n jffs2_clear_xattr_subsystem \u003c--- free again\n-----------------------------------------------------------\n\nAn error is returned in jffs2_do_mount_fs(). If the error is returned\nby jffs2_sum_init(), the jffs2_clear_xattr_subsystem() does not need to\nbe executed. If the error is returned by jffs2_build_filesystem(), the\njffs2_clear_xattr_subsystem() also does not need to be executed again.\nSo move jffs2_clear_xattr_subsystem() from \u0027out_inohash\u0027 to \u0027out_root\u0027\nto fix this UAF problem."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The bug is reached only through the local mount path (mount \u2192 jffs2_get_tree \u2192 get_tree_mtd \u2192 jffs2_fill_super \u2192 jffs2_do_fill_super \u2192 jffs2_do_mount_fs \u2192 jffs2_build_filesystem), parsing an MTD/JFFS2 image; there is no network-facing consumer.\nAC:L - An attacker who crafts the image fully controls the trigger\u2014place valid XREF/XATTR nodes in early eraseblocks so jffs2_alloc_xattr_ref() populates xref_temp, then make a later block fail jffs2_scan_eraseblock()\u2014with no race or attacker-uncontrollable condition.\nPR:N - The attacker needs no account on the target; they only supply the crafted JFFS2/MTD image (firmware blob, flash/SD contents), and CAP_SYS_ADMIN belongs to the victim or tooling that mounts it, matching the crafted-filesystem-image pattern.\nUI:R - Exploitation requires a victim (root, firmware updater, or automounter) to mount the attacker-supplied JFFS2 image so the failing scan hits the double clear_xattr path.\nS:U - The use-after-free corrupts kernel slab memory within the same host OS security authority; no VM escape, IOMMU bypass, or other cross-boundary compromise occurs.\nC:H - jffs2_clear_xattr_subsystem() frees xref_temp without NULLing it, so the second call reads ref-\u003enext from freed jffs2_xattr_ref slab objects; per guidance a UAF enables arbitrary kernel memory disclosure.\nI:H - The second pass double-frees attacker-populated jffs2_xattr_ref objects, enabling classic heap spraying and overlapping allocations for arbitrary write / control-flow hijack.\nA:H - The KASAN-confirmed use-after-free during mount produces a kernel oops/panic even without full exploitation, and is repeatable on every mount of the crafted image."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T08:48:47.063Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/9150cb625b46f68d524f4cfd491f1aafc23e10a9"
},
{
"url": "https://git.kernel.org/stable/c/3bd2454162ec6bbb5503233c804fce6e4b6dcec5"
},
{
"url": "https://git.kernel.org/stable/c/c3b07c875fa8f906f932976460fd14798596f101"
},
{
"url": "https://git.kernel.org/stable/c/30bf7244acf32f19cb722c39f7bc1c2a9f300422"
},
{
"url": "https://git.kernel.org/stable/c/7bb7428dd73991bf4b3a7a61b493ca50046c2b13"
},
{
"url": "https://git.kernel.org/stable/c/7a75740206af5f17e9f3efa384211cba70213da1"
},
{
"url": "https://git.kernel.org/stable/c/22327bd7988f21de3a53c1373f3b81542bfe1f44"
},
{
"url": "https://git.kernel.org/stable/c/8c0f024f29e055840a5a89fe23b96ae3f921afed"
},
{
"url": "https://git.kernel.org/stable/c/4c7c44ee1650677fbe89d86edbad9497b7679b5c"
}
],
"title": "jffs2: fix use-after-free in jffs2_clear_xattr_subsystem",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2021-47656",
"datePublished": "2025-02-26T01:54:20.069Z",
"dateReserved": "2025-02-26T01:48:21.521Z",
"dateUpdated": "2026-08-05T08:48:47.063Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Trend slope:
-
(linear fit over daily sighting counts)
Show additional events:
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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.
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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.
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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.
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