{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23393","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-01-13T15:37:46.011Z","datePublished":"2026-03-25T10:33:17.407Z","dateUpdated":"2026-08-05T12:21:24.386Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T12:21:24.386Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbridge: cfm: Fix race condition in peer_mep deletion\n\nWhen a peer MEP is being deleted, cancel_delayed_work_sync() is called\non ccm_rx_dwork before freeing. However, br_cfm_frame_rx() runs in\nsoftirq context under rcu_read_lock (without RTNL) and can re-schedule\nccm_rx_dwork via ccm_rx_timer_start() between cancel_delayed_work_sync()\nreturning and kfree_rcu() being called.\n\nThe following is a simple race scenario:\n\n           cpu0                                     cpu1\n\nmep_delete_implementation()\n  cancel_delayed_work_sync(ccm_rx_dwork);\n                                           br_cfm_frame_rx()\n                                             // peer_mep still in hlist\n                                             if (peer_mep->ccm_defect)\n                                               ccm_rx_timer_start()\n                                                 queue_delayed_work(ccm_rx_dwork)\n  hlist_del_rcu(&peer_mep->head);\n  kfree_rcu(peer_mep, rcu);\n                                           ccm_rx_work_expired()\n                                             // on freed peer_mep\n\nTo prevent this, cancel_delayed_work_sync() is replaced with\ndisable_delayed_work_sync() in both peer MEP deletion paths, so\nthat subsequent queue_delayed_work() calls from br_cfm_frame_rx()\nare silently rejected.\n\nThe cc_peer_disable() helper retains cancel_delayed_work_sync()\nbecause it is also used for the CC enable/disable toggle path where\nthe work must remain re-schedulable."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerability requires local access to configure bridge CFM via netlink (RTM_SETLINK requiring CAP_NET_ADMIN) and send CFM frames on virtual bridge interfaces, all achievable from a local user namespace.\nAC:L - The attacker controls both sides of the race — they can simultaneously delete peer MEPs via netlink and send CFM frames on virtual bridge port interfaces, making the race reliably triggerable.\nPR:L - CAP_NET_ADMIN is required for bridge CFM configuration, but it is obtainable via user namespaces (unshare -Urn) since netlink_net_capable checks against the namespace's user_ns.\nUI:N - No user interaction is needed; the attacker can set up the bridge, configure CFM, and trigger the race entirely autonomously.\nS:U - This is a standard kernel use-after-free with no cross-boundary impact such as VM escape or IOMMU bypass.\nC:H - The use-after-free allows the attacker to read freed memory that may be reallocated with controlled data, enabling arbitrary kernel memory disclosure.\nI:H - The use-after-free on the peer_mep structure enables heap spraying and potential arbitrary write primitives through control of the freed object's contents.\nA:H - The use-after-free causes ccm_rx_work_expired to operate on freed memory, reliably causing a kernel crash or panic."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bridge/br_cfm.c"],"versions":[{"version":"dc32cbb3dbd7da38c700d6e0fc6354df24920525","lessThan":"e89dbd2736a45f0507949af4748cbbf3ff793146","status":"affected","versionType":"git"},{"version":"dc32cbb3dbd7da38c700d6e0fc6354df24920525","lessThan":"d8f35767bacb3c7769d470a41cf161e3f3c07e70","status":"affected","versionType":"git"},{"version":"dc32cbb3dbd7da38c700d6e0fc6354df24920525","lessThan":"1fd81151f65927fd9edb8ecd12ad45527dbbe5ab","status":"affected","versionType":"git"},{"version":"dc32cbb3dbd7da38c700d6e0fc6354df24920525","lessThan":"3715a00855316066cdda69d43648336367422127","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/bridge/br_cfm.c"],"versions":[{"version":"5.11","status":"affected"},{"version":"0","lessThan":"5.11","status":"unaffected","versionType":"semver"},{"version":"6.12.78","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.20","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"6.19.10","lessThanOrEqual":"6.19.*","status":"unaffected","versionType":"semver"},{"version":"7.0","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.18.20"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"6.19.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.11","versionEndExcluding":"7.0"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/e89dbd2736a45f0507949af4748cbbf3ff793146"},{"url":"https://git.kernel.org/stable/c/d8f35767bacb3c7769d470a41cf161e3f3c07e70"},{"url":"https://git.kernel.org/stable/c/1fd81151f65927fd9edb8ecd12ad45527dbbe5ab"},{"url":"https://git.kernel.org/stable/c/3715a00855316066cdda69d43648336367422127"}],"title":"bridge: cfm: Fix race condition in peer_mep deletion","x_generator":{"engine":"bippy-1.2.0"}}}}