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EUVD-2026-344522

European Vulnerability Database identifier assigned by ENISA

Reserved

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.

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{
  "assigner": "ENISA",
  "date_reserved": "2026-10-02T07:56:41.930126+00:00",
  "id": "EUVD-2026-344522"
}

CVE-2021-47588 (GCVE-0-2021-47588)

Vulnerability from cvelistv5 – Published: 2024-06-19 14:53 – Updated: 2026-08-05 08:48

Title

sit: do not call ipip6_dev_free() from sit_init_net()

Summary

In the Linux kernel, the following vulnerability has been resolved: sit: do not call ipip6_dev_free() from sit_init_net() ipip6_dev_free is sit dev->priv_destructor, already called by register_netdevice() if something goes wrong. Alternative would be to make ipip6_dev_free() robust against multiple invocations, but other drivers do not implement this strategy. syzbot reported: dst_release underflow WARNING: CPU: 0 PID: 5059 at net/core/dst.c:173 dst_release+0xd8/0xe0 net/core/dst.c:173 Modules linked in: CPU: 1 PID: 5059 Comm: syz-executor.4 Not tainted 5.16.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:dst_release+0xd8/0xe0 net/core/dst.c:173 Code: 4c 89 f2 89 d9 31 c0 5b 41 5e 5d e9 da d5 44 f9 e8 1d 90 5f f9 c6 05 87 48 c6 05 01 48 c7 c7 80 44 99 8b 31 c0 e8 e8 67 29 f9 <0f> 0b eb 85 0f 1f 40 00 53 48 89 fb e8 f7 8f 5f f9 48 83 c3 a8 48 RSP: 0018:ffffc9000aa5faa0 EFLAGS: 00010246 RAX: d6894a925dd15a00 RBX: 00000000ffffffff RCX: 0000000000040000 RDX: ffffc90005e19000 RSI: 000000000003ffff RDI: 0000000000040000 RBP: 0000000000000000 R08: ffffffff816a1f42 R09: ffffed1017344f2c R10: ffffed1017344f2c R11: 0000000000000000 R12: 0000607f462b1358 R13: 1ffffffff1bfd305 R14: ffffe8ffffcb1358 R15: dffffc0000000000 FS: 00007f66c71a2700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f88aaed5058 CR3: 0000000023e0f000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> dst_cache_destroy+0x107/0x1e0 net/core/dst_cache.c:160 ipip6_dev_free net/ipv6/sit.c:1414 [inline] sit_init_net+0x229/0x550 net/ipv6/sit.c:1936 ops_init+0x313/0x430 net/core/net_namespace.c:140 setup_net+0x35b/0x9d0 net/core/net_namespace.c:326 copy_net_ns+0x359/0x5c0 net/core/net_namespace.c:470 create_new_namespaces+0x4ce/0xa00 kernel/nsproxy.c:110 unshare_nsproxy_namespaces+0x11e/0x180 kernel/nsproxy.c:226 ksys_unshare+0x57d/0xb50 kernel/fork.c:3075 __do_sys_unshare kernel/fork.c:3146 [inline] __se_sys_unshare kernel/fork.c:3144 [inline] __x64_sys_unshare+0x34/0x40 kernel/fork.c:3144 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f66c882ce99 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f66c71a2168 EFLAGS: 00000246 ORIG_RAX: 0000000000000110 RAX: ffffffffffffffda RBX: 00007f66c893ff60 RCX: 00007f66c882ce99 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000048040200 RBP: 00007f66c8886ff1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fff6634832f R14: 00007f66c71a2300 R15: 0000000000022000 </TASK>

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2024-09-10 17:12 UTC

Assigner

Linux mitre root Scorecard

References

6 references

URL	Tags
https://git.kernel.org/stable/c/4e1797914d8f22372…
https://git.kernel.org/stable/c/e56b65c1e74d7f706…
https://git.kernel.org/stable/c/ad0ed314d6167b212…
https://git.kernel.org/stable/c/6f46c59e60b64620d…
https://git.kernel.org/stable/c/44a6c846bc3a7efe7…
https://git.kernel.org/stable/c/e28587cc491ef0f3c…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: cf124db566e6b036b8bcbe8decbed740bdfac8c6 , < 4e1797914d8f223726ff6ae5ece4f97d73f21bab (git) Affected: cf124db566e6b036b8bcbe8decbed740bdfac8c6 , < e56b65c1e74d7f706d74b51baba15187be2fb4b5 (git) Affected: cf124db566e6b036b8bcbe8decbed740bdfac8c6 , < ad0ed314d6167b212939e3839428ba0c8bb16adb (git) Affected: cf124db566e6b036b8bcbe8decbed740bdfac8c6 , < 6f46c59e60b64620d5d386c8ee2eaa11ebe3b595 (git) Affected: cf124db566e6b036b8bcbe8decbed740bdfac8c6 , < 44a6c846bc3a7efe7d394bab8b2ae3b7f580e190 (git) Affected: cf124db566e6b036b8bcbe8decbed740bdfac8c6 , < e28587cc491ef0f3c51258fdc87fbc386b1d4c59 (git) Affected: 95876855a55072572895a236b156ffb357fd5538 (git) Affected: 4.11.9 , < 4.12 (semver)
Linux	Linux	Affected: 4.12 Unaffected: 0 , < 4.12 (semver) Unaffected: 4.14.259 , ≤ 4.14.* (semver) Unaffected: 4.19.222 , ≤ 4.19.* (semver) Unaffected: 5.4.168 , ≤ 5.4.* (semver) Unaffected: 5.10.88 , ≤ 5.10.* (semver) Unaffected: 5.15.11 , ≤ 5.15.* (semver) Unaffected: 5.16 , ≤ * (original_commit_for_fix)

Show details on NVD website

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{
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            "url": "https://git.kernel.org/stable/c/ad0ed314d6167b212939e3839428ba0c8bb16adb"
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            "url": "https://git.kernel.org/stable/c/44a6c846bc3a7efe7d394bab8b2ae3b7f580e190"
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            "url": "https://git.kernel.org/stable/c/e28587cc491ef0f3c51258fdc87fbc386b1d4c59"
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        "title": "CVE Program Container"
      },
      {
        "metrics": [
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                "id": "CVE-2021-47588",
                "options": [
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                  },
                  {
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                  },
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                ],
                "role": "CISA Coordinator",
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          "product": "Linux",
          "programFiles": [
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              "version": "5.16",
              "versionType": "original_commit_for_fix"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsit: do not call ipip6_dev_free() from sit_init_net()\n\nipip6_dev_free is sit dev-\u003epriv_destructor, already called\nby register_netdevice() if something goes wrong.\n\nAlternative would be to make ipip6_dev_free() robust against\nmultiple invocations, but other drivers do not implement this\nstrategy.\n\nsyzbot reported:\n\ndst_release underflow\nWARNING: CPU: 0 PID: 5059 at net/core/dst.c:173 dst_release+0xd8/0xe0 net/core/dst.c:173\nModules linked in:\nCPU: 1 PID: 5059 Comm: syz-executor.4 Not tainted 5.16.0-rc5-syzkaller #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011\nRIP: 0010:dst_release+0xd8/0xe0 net/core/dst.c:173\nCode: 4c 89 f2 89 d9 31 c0 5b 41 5e 5d e9 da d5 44 f9 e8 1d 90 5f f9 c6 05 87 48 c6 05 01 48 c7 c7 80 44 99 8b 31 c0 e8 e8 67 29 f9 \u003c0f\u003e 0b eb 85 0f 1f 40 00 53 48 89 fb e8 f7 8f 5f f9 48 83 c3 a8 48\nRSP: 0018:ffffc9000aa5faa0 EFLAGS: 00010246\nRAX: d6894a925dd15a00 RBX: 00000000ffffffff RCX: 0000000000040000\nRDX: ffffc90005e19000 RSI: 000000000003ffff RDI: 0000000000040000\nRBP: 0000000000000000 R08: ffffffff816a1f42 R09: ffffed1017344f2c\nR10: ffffed1017344f2c R11: 0000000000000000 R12: 0000607f462b1358\nR13: 1ffffffff1bfd305 R14: ffffe8ffffcb1358 R15: dffffc0000000000\nFS:  00007f66c71a2700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 00007f88aaed5058 CR3: 0000000023e0f000 CR4: 00000000003506f0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n \u003cTASK\u003e\n dst_cache_destroy+0x107/0x1e0 net/core/dst_cache.c:160\n ipip6_dev_free net/ipv6/sit.c:1414 [inline]\n sit_init_net+0x229/0x550 net/ipv6/sit.c:1936\n ops_init+0x313/0x430 net/core/net_namespace.c:140\n setup_net+0x35b/0x9d0 net/core/net_namespace.c:326\n copy_net_ns+0x359/0x5c0 net/core/net_namespace.c:470\n create_new_namespaces+0x4ce/0xa00 kernel/nsproxy.c:110\n unshare_nsproxy_namespaces+0x11e/0x180 kernel/nsproxy.c:226\n ksys_unshare+0x57d/0xb50 kernel/fork.c:3075\n __do_sys_unshare kernel/fork.c:3146 [inline]\n __se_sys_unshare kernel/fork.c:3144 [inline]\n __x64_sys_unshare+0x34/0x40 kernel/fork.c:3144\n do_syscall_x64 arch/x86/entry/common.c:50 [inline]\n do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80\n entry_SYSCALL_64_after_hwframe+0x44/0xae\nRIP: 0033:0x7f66c882ce99\nCode: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 \u003c48\u003e 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48\nRSP: 002b:00007f66c71a2168 EFLAGS: 00000246 ORIG_RAX: 0000000000000110\nRAX: ffffffffffffffda RBX: 00007f66c893ff60 RCX: 00007f66c882ce99\nRDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000048040200\nRBP: 00007f66c8886ff1 R08: 0000000000000000 R09: 0000000000000000\nR10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000\nR13: 00007fff6634832f R14: 00007f66c71a2300 R15: 0000000000022000\n \u003c/TASK\u003e"
        }
      ],
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        {
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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              "value": "AV:L - The bug is reached only through local netns creation (unshare/clone \u2192 copy_net_ns \u2192 setup_net \u2192 sit_init_net), not by processing remote/adjacent packets.\nAC:L - An attacker can reliably force the post-ndo_init register_netdev() failure (e.g. memory pressure failing netdev_register_kobject) so priv_destructor runs, then sit_init_net calls ipip6_dev_free() again; no race or layout outside their control is required.\nPR:L - Creating a netns needs CAP_SYS_ADMIN in the user namespace (ns_capable), which an unprivileged user obtains via user+net namespaces (unshare -Urn); CONFIG_IPV6_SIT defaults to y and fallback tunnels are created in all netns by default.\nUI:N - The attacker triggers the failing sit0 registration entirely with their own unshare/clone; no victim action is required.\nS:U - This is a standard in-kernel double-free/UAF within the same OS security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - ipip6_dev_free() is invoked twice, double-freeing percpu dst_cache/tstats and UAFing the dst_cache; reclaim of that memory enables attacker-controlled reads and arbitrary kernel disclosure.\nI:H - The same double-free/UAF of percpu allocations yields heap corruption that can be sprayed for arbitrary write and control-flow hijacking primitives.\nA:H - The double-free produces dst_release underflow warnings/oopses (as in the syzbot report) and can panic or crash the kernel even without full exploitation."
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        },
        {
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      ],
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        "engine": "bippy-1.2.0"
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2021-47588",
    "datePublished": "2024-06-19T14:53:52.909Z",
    "dateReserved": "2024-05-24T15:11:00.732Z",
    "dateUpdated": "2026-08-05T08:48:30.684Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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.
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EUVD-2026-344522

CVE-2021-47588 (GCVE-0-2021-47588)

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