CVE-2026-43455 (GCVE-0-2026-43455)

Vulnerability from cvelistv5 – Published: 2026-05-08 14:22 – Updated: 2026-05-11 22:24
VLAI?
Title
mctp: route: hold key->lock in mctp_flow_prepare_output()
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 67737c457281dd199ceb9e31b6ba7efd3bfe566d , < 47893166bc5611ee9a20de6b8d2933b2320fb772 (git)
Affected: 67737c457281dd199ceb9e31b6ba7efd3bfe566d , < 86f5334fcb48a5b611c33364ab52ca684d0f6d91 (git)
Affected: 67737c457281dd199ceb9e31b6ba7efd3bfe566d , < 0695712f3a6f1a48915f95767cfb42077683dcdc (git)
Affected: 67737c457281dd199ceb9e31b6ba7efd3bfe566d , < 925a5ffd99cddd7a7e41d5ad120c7a2c6d50260f (git)
Affected: 67737c457281dd199ceb9e31b6ba7efd3bfe566d , < 8d27d9b260dd19c1b519e1a13de6448f9984e30e (git)
Affected: 67737c457281dd199ceb9e31b6ba7efd3bfe566d , < 7d86aa41c073c4e7eb75fd2e674f1fd8f289728a (git)
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    Linux Linux Affected: 5.16
Unaffected: 0 , < 5.16 (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.78 , ≤ 6.12.* (semver)
Unaffected: 6.18.19 , ≤ 6.18.* (semver)
Unaffected: 6.19.9 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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      "cpeApplicability": [
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      "descriptions": [
        {
          "lang": "en",
          "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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      "providerMetadata": {
        "dateUpdated": "2026-05-11T22:24:55.256Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "cveId": "CVE-2026-43455",
    "datePublished": "2026-05-08T14:22:19.375Z",
    "dateReserved": "2026-05-01T14:12:56.010Z",
    "dateUpdated": "2026-05-11T22:24:55.256Z",
    "state": "PUBLISHED"
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