{"id":"CVE-2026-63874","state":"PUBLISHED","title":"net: mctp: usb: fix race between urb completion and rx_retry cancellation","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mctp: usb: fix race between urb completion and rx_retry cancellation\n\nIt's possible that sequencing between setting ->stopped and cancelling\nthe rx_retry work (in ndo_stop) could leave us with an urb queued:\n\n    T1: ndo_stop                  T2: rx_retry_work\n    ------------                  ----------------\n                                  LD: ->stopped => false\n    ST: ->stopped <= true\n    usb_kill_urb()\n                                  mctp_usb_rx_queue()\n                                    usb_submit_urb()\n    cancel_delayed_work_sync()\n\nThat urb completion can then re-schedule rx_retry_work.\n\nStrenghen the sequencing between the stop (preventing another requeue)\nand the cancel by updating both atomically under a new rx lock. After\nsetting ->rx_stopped, and cancelling pending work, we know that the\nrequeue cannot occur, so all that's left is killing any pending urb.","publishedAt":"2026-07-19T14:18:41.907Z","updatedAt":"2026-08-05T12:36:47.817Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0791c0327a6e4e7691d6fc5ad334c215de04dcc9","status":"affected","lessThan":"9c46f3ee1837f6881cb99a52ffecb2760f11dc73","versionType":"git"},{"version":"0791c0327a6e4e7691d6fc5ad334c215de04dcc9","status":"affected","lessThan":"d90feaa3f74bea8dafb6494631a194c70e547d94","versionType":"git"},{"version":"0791c0327a6e4e7691d6fc5ad334c215de04dcc9","status":"affected","lessThan":"54665dce982689e2fd99b32e9a0dcc204fda8a51","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/mctp/mctp-usb.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.18.36","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.13","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/mctp/mctp-usb.c"]}],"references":["https://git.kernel.org/stable/c/9c46f3ee1837f6881cb99a52ffecb2760f11dc73","https://git.kernel.org/stable/c/d90feaa3f74bea8dafb6494631a194c70e547d94","https://git.kernel.org/stable/c/54665dce982689e2fd99b32e9a0dcc204fda8a51"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/63xxx/CVE-2026-63874.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-63874","state":"PUBLISHED","datePublished":"2026-07-19T14:18:41.907Z","dateUpdated":"2026-08-05T12:36:47.817Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T07:54:57.017Z"},"containers":{"cna":{"title":"net: mctp: usb: fix race between urb completion and rx_retry cancellation","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: mctp: usb: fix race between urb completion and rx_retry cancellation\n\nIt's possible that sequencing between setting ->stopped and cancelling\nthe rx_retry work (in ndo_stop) could leave us with an urb queued:\n\n    T1: ndo_stop                  T2: rx_retry_work\n    ------------                  ----------------\n                                  LD: ->stopped => false\n    ST: ->stopped <= true\n    usb_kill_urb()\n                                  mctp_usb_rx_queue()\n                                    usb_submit_urb()\n    cancel_delayed_work_sync()\n\nThat urb completion can then re-schedule rx_retry_work.\n\nStrenghen the sequencing between the stop (preventing another requeue)\nand the cancel by updating both atomically under a new rx lock. After\nsetting ->rx_stopped, and cancelling pending work, we know that the\nrequeue cannot occur, so all that's left is killing any pending urb."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"0791c0327a6e4e7691d6fc5ad334c215de04dcc9","status":"affected","lessThan":"9c46f3ee1837f6881cb99a52ffecb2760f11dc73","versionType":"git"},{"version":"0791c0327a6e4e7691d6fc5ad334c215de04dcc9","status":"affected","lessThan":"d90feaa3f74bea8dafb6494631a194c70e547d94","versionType":"git"},{"version":"0791c0327a6e4e7691d6fc5ad334c215de04dcc9","status":"affected","lessThan":"54665dce982689e2fd99b32e9a0dcc204fda8a51","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/mctp/mctp-usb.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.18.36","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.13","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/mctp/mctp-usb.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/9c46f3ee1837f6881cb99a52ffecb2760f11dc73"},{"url":"https://git.kernel.org/stable/c/d90feaa3f74bea8dafb6494631a194c70e547d94"},{"url":"https://git.kernel.org/stable/c/54665dce982689e2fd99b32e9a0dcc204fda8a51"}],"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 race is hit in `mctp_usb_stop()` (`ndo_stop`) during netdev teardown, which is reachable via local RTNETLINK (`ip link set down`) or USB disconnect; it is not reachable from remote network input. Per the uncertainty rule, Local is chosen over Physical.\nAC:L - An attacker can control both sides of the race by inducing RX ENOMEM to schedule `rx_retry_work` (memory pressure) and concurrently triggering netdev stop/disconnect, retrying timing until the window between `stopped=true` and `cancel_delayed_work_sync()` is won.\nPR:L - Triggering `ndo_stop` through RTNETLINK requires `CAP_NET_ADMIN`, which is obtainable in an unprivileged user namespace; a physical USB disconnect path needs no software privileges, but PR:L is the higher-severity choice when uncertain.\nUI:N - Exploitation does not require any victim user action beyond the attacker’s own interface teardown/disconnect and memory-pressure timing.\nS:U - Impact is kernel memory corruption/UAF within the same kernel security boundary, not a cross-boundary escape such as guest-to-host or sandbox breakout.\nC:H - Winning the race leaves RX URBs/completions running after `usb_free_urb()` and `free_netdev()`, producing a use-after-free on `net_device`, `urb`, and `sk_buff` objects that can be turned into arbitrary kernel memory disclosure.\nI:H - The post-teardown UAF on heap-allocated driver/netdev/USB objects provides exploitable write primitives (re-submitted URBs, corrupted completion handlers) suitable for control-flow hijack and privilege escalation.\nA:H - The bug reliably causes kernel crashes (oops/panic) when freed URBs/netdevs are touched by completion handlers or rescheduled `rx_retry_work`, even before full exploitation."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:36:47.817Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.18.36"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.0.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}