{"id":"CVE-2026-43455","state":"PUBLISHED","title":"mctp: route: hold key->lock in mctp_flow_prepare_output()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmctp: route: hold key->lock in mctp_flow_prepare_output()\n\nmctp_flow_prepare_output() checks key->dev and may call\nmctp_dev_set_key(), but it does not hold key->lock while doing so.\n\nmctp_dev_set_key() and mctp_dev_release_key() are annotated with\n__must_hold(&key->lock), so key->dev access is intended to be\nserialized by key->lock. The mctp_sendmsg() transmit path reaches\nmctp_flow_prepare_output() via mctp_local_output() -> mctp_dst_output()\nwithout holding key->lock, 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->dev)  // sees NULL\n                                        mctp_flow_prepare_output(\n                                            key, devB)\n                                          if (!key->dev)  // still NULL\n                                          mctp_dev_set_key(devB, key)\n                                            mctp_dev_hold(devB)\n                                            key->dev = devB\n    mctp_dev_set_key(devA, key)\n      mctp_dev_hold(devA)\n      key->dev = devA   // overwrites devB\n\nNow both devA and devB references were acquired, but only the final\nkey->dev 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->lock around the key->dev check and\nmctp_dev_set_key() call.","publishedAt":"2026-05-08T14:22:19.375Z","updatedAt":"2026-05-11T22:24:55.256Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"47893166bc5611ee9a20de6b8d2933b2320fb772","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"86f5334fcb48a5b611c33364ab52ca684d0f6d91","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"0695712f3a6f1a48915f95767cfb42077683dcdc","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"925a5ffd99cddd7a7e41d5ad120c7a2c6d50260f","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"8d27d9b260dd19c1b519e1a13de6448f9984e30e","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"7d86aa41c073c4e7eb75fd2e674f1fd8f289728a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/mctp/route.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.16","versionType":"semver"},{"version":"6.1.167","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.19","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/mctp/route.c"]}],"references":["https://git.kernel.org/stable/c/47893166bc5611ee9a20de6b8d2933b2320fb772","https://git.kernel.org/stable/c/86f5334fcb48a5b611c33364ab52ca684d0f6d91","https://git.kernel.org/stable/c/0695712f3a6f1a48915f95767cfb42077683dcdc","https://git.kernel.org/stable/c/925a5ffd99cddd7a7e41d5ad120c7a2c6d50260f","https://git.kernel.org/stable/c/8d27d9b260dd19c1b519e1a13de6448f9984e30e","https://git.kernel.org/stable/c/7d86aa41c073c4e7eb75fd2e674f1fd8f289728a"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43455.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43455","state":"PUBLISHED","datePublished":"2026-05-08T14:22:19.375Z","dateUpdated":"2026-05-11T22:24:55.256Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:56.010Z"},"containers":{"cna":{"title":"mctp: route: hold key->lock in mctp_flow_prepare_output()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmctp: route: hold key->lock in mctp_flow_prepare_output()\n\nmctp_flow_prepare_output() checks key->dev and may call\nmctp_dev_set_key(), but it does not hold key->lock while doing so.\n\nmctp_dev_set_key() and mctp_dev_release_key() are annotated with\n__must_hold(&key->lock), so key->dev access is intended to be\nserialized by key->lock. The mctp_sendmsg() transmit path reaches\nmctp_flow_prepare_output() via mctp_local_output() -> mctp_dst_output()\nwithout holding key->lock, 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->dev)  // sees NULL\n                                        mctp_flow_prepare_output(\n                                            key, devB)\n                                          if (!key->dev)  // still NULL\n                                          mctp_dev_set_key(devB, key)\n                                            mctp_dev_hold(devB)\n                                            key->dev = devB\n    mctp_dev_set_key(devA, key)\n      mctp_dev_hold(devA)\n      key->dev = devA   // overwrites devB\n\nNow both devA and devB references were acquired, but only the final\nkey->dev 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->lock around the key->dev check and\nmctp_dev_set_key() call."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"47893166bc5611ee9a20de6b8d2933b2320fb772","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"86f5334fcb48a5b611c33364ab52ca684d0f6d91","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"0695712f3a6f1a48915f95767cfb42077683dcdc","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"925a5ffd99cddd7a7e41d5ad120c7a2c6d50260f","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"8d27d9b260dd19c1b519e1a13de6448f9984e30e","versionType":"git"},{"version":"67737c457281dd199ceb9e31b6ba7efd3bfe566d","status":"affected","lessThan":"7d86aa41c073c4e7eb75fd2e674f1fd8f289728a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/mctp/route.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.16","versionType":"semver"},{"version":"6.1.167","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.19","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/mctp/route.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/47893166bc5611ee9a20de6b8d2933b2320fb772"},{"url":"https://git.kernel.org/stable/c/86f5334fcb48a5b611c33364ab52ca684d0f6d91"},{"url":"https://git.kernel.org/stable/c/0695712f3a6f1a48915f95767cfb42077683dcdc"},{"url":"https://git.kernel.org/stable/c/925a5ffd99cddd7a7e41d5ad120c7a2c6d50260f"},{"url":"https://git.kernel.org/stable/c/8d27d9b260dd19c1b519e1a13de6448f9984e30e"},{"url":"https://git.kernel.org/stable/c/7d86aa41c073c4e7eb75fd2e674f1fd8f289728a"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T22:24:55.256Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.1.167"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.6.130"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.18.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.19.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}