FKIE_CVE-2026-43455

Vulnerability from fkie_nvd - Published: 2026-05-08 15:16 - Updated: 2026-05-20 18:04
Severity
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: mctp: route: hold key->lock in mctp_flow_prepare_output() mctp_flow_prepare_output() checks key->dev and may call mctp_dev_set_key(), but it does not hold key->lock while doing so. mctp_dev_set_key() and mctp_dev_release_key() are annotated with __must_hold(&key->lock), so key->dev access is intended to be serialized by key->lock. The mctp_sendmsg() transmit path reaches mctp_flow_prepare_output() via mctp_local_output() -> mctp_dst_output() without holding key->lock, so the check-and-set sequence is racy. Example interleaving: CPU0 CPU1 ---- ---- mctp_flow_prepare_output(key, devA) if (!key->dev) // sees NULL mctp_flow_prepare_output( key, devB) if (!key->dev) // still NULL mctp_dev_set_key(devB, key) mctp_dev_hold(devB) key->dev = devB mctp_dev_set_key(devA, key) mctp_dev_hold(devA) key->dev = devA // overwrites devB Now both devA and devB references were acquired, but only the final key->dev value is tracked for release. One reference can be lost, causing a resource leak as mctp_dev_release_key() would only decrease the reference on one dev. Fix by taking key->lock around the key->dev check and mctp_dev_set_key() call.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0695712f3a6f1a48915f95767cfb42077683dcdcPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/47893166bc5611ee9a20de6b8d2933b2320fb772Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7d86aa41c073c4e7eb75fd2e674f1fd8f289728aPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/86f5334fcb48a5b611c33364ab52ca684d0f6d91Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8d27d9b260dd19c1b519e1a13de6448f9984e30ePatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/925a5ffd99cddd7a7e41d5ad120c7a2c6d50260fPatch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
To clipboard 

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmctp: route: hold key-\u003elock in mctp_flow_prepare_output()\n\nmctp_flow_prepare_output() checks key-\u003edev and may call\nmctp_dev_set_key(), but it does not hold key-\u003elock while doing so.\n\nmctp_dev_set_key() and mctp_dev_release_key() are annotated with\n__must_hold(\u0026key-\u003elock), so key-\u003edev access is intended to be\nserialized by key-\u003elock. The mctp_sendmsg() transmit path reaches\nmctp_flow_prepare_output() via mctp_local_output() -\u003e mctp_dst_output()\nwithout holding key-\u003elock, so the check-and-set sequence is racy.\n\nExample interleaving:\n\n  CPU0                                  CPU1\n  ----                                  ----\n  mctp_flow_prepare_output(key, devA)\n    if (!key-\u003edev)  // sees NULL\n                                        mctp_flow_prepare_output(\n                                            key, devB)\n                                          if (!key-\u003edev)  // still NULL\n                                          mctp_dev_set_key(devB, key)\n                                            mctp_dev_hold(devB)\n                                            key-\u003edev = devB\n    mctp_dev_set_key(devA, key)\n      mctp_dev_hold(devA)\n      key-\u003edev = devA   // overwrites devB\n\nNow both devA and devB references were acquired, but only the final\nkey-\u003edev value is tracked for release. One reference can be lost,\ncausing a resource leak as mctp_dev_release_key() would only decrease\nthe reference on one dev.\n\nFix by taking key-\u003elock around the key-\u003edev check and\nmctp_dev_set_key() call."
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  "id": "CVE-2026-43455",
  "lastModified": "2026-05-20T18:04:20.973",
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          "attackVector": "LOCAL",
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          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
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        "impactScore": 3.6,
        "source": "nvd@nist.gov",
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  "published": "2026-05-08T15:16:58.263",
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