{"id":"CVE-2026-74692","state":"PUBLISHED","title":"net/smc: fix TOCTOU race between smc_listen_out() and listener close","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix TOCTOU race between smc_listen_out() and listener close\n\nsmc_listen_out() reads lsmc->sk.sk_state without the listener lock,\nthen acquires lock_sock_nested() only after the check passes. This\nopens a window where smc_close_active() can transition the listener\nto SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept\nqueue, and release the lock, all between the lockless read and the\ndelayed lock acquisition:\n\n  smc_listen_work (smc_hs_wq)          smc_close_active()\n  -------------------------------      -------------------------\n  release_sock(child)\n  if (sk_state == SMC_LISTEN) TRUE\n                                        lock_sock(listener)\n                                        sk_state = SMC_CLOSED\n                                        smc_close_cleanup_listen()\n                                        release_sock(listener)\n                                        flush_work(tcp_listen_work)\n  lock_sock_nested(listener)\n  smc_accept_enqueue(listener, child) /* child enqueued on dead listener */\n\nsmc_close_active() flushes only tcp_listen_work. Work items already\ndispatched onto smc_hs_wq for the CLC handshake continue running\nunguarded. smc_accept_enqueue() takes a sock_hold() on the child that\nis never released, so the child smc_sock, its clcsock, and the\nreference all leak. A remote peer that opens TCP connections while the\nserver calls close() can exhaust kernel memory.\n\nMove lock_sock_nested() to before the sk_state check so that the test\nand the enqueue are atomic under the listener lock.","publishedAt":"2026-08-22T15:32:55.873Z","updatedAt":"2026-10-16T19:16:09.513Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"53c7938d8bcfde3296ec1a347ba2a9393c1fdcfa","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"feb71634bb1abab3e8fb5cde874b27001cc1282e","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"01865e1ddb126b25ac9eba5cdd7ec49e11183a64","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"00f89433777236ced4771211047fb5d4cd581cea","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"78e5ebcd1c10ed7c8bda0a99e0abd5b62da86d67","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"ff5bcd804b5bc5c64736b7d318c20e12ea9506b8","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"185a4caeecabc150106deda1da170b09f2ad803f","versionType":"git"},{"version":"d1d004585b40c212b338fc8a40cbaaf230ea4703","status":"affected","versionType":"git"},{"version":"4.19.299","status":"affected","lessThan":"4.20","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/af_smc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.1","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.152","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/af_smc.c"]}],"references":["https://git.kernel.org/stable/c/53c7938d8bcfde3296ec1a347ba2a9393c1fdcfa","https://git.kernel.org/stable/c/feb71634bb1abab3e8fb5cde874b27001cc1282e","https://git.kernel.org/stable/c/01865e1ddb126b25ac9eba5cdd7ec49e11183a64","https://git.kernel.org/stable/c/00f89433777236ced4771211047fb5d4cd581cea","https://git.kernel.org/stable/c/78e5ebcd1c10ed7c8bda0a99e0abd5b62da86d67","https://git.kernel.org/stable/c/ff5bcd804b5bc5c64736b7d318c20e12ea9506b8","https://git.kernel.org/stable/c/185a4caeecabc150106deda1da170b09f2ad803f"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74692.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74692","state":"PUBLISHED","datePublished":"2026-08-22T15:32:55.873Z","dateUpdated":"2026-10-16T19:16:09.513Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.926Z"},"containers":{"cna":{"title":"net/smc: fix TOCTOU race between smc_listen_out() and listener close","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix TOCTOU race between smc_listen_out() and listener close\n\nsmc_listen_out() reads lsmc->sk.sk_state without the listener lock,\nthen acquires lock_sock_nested() only after the check passes. This\nopens a window where smc_close_active() can transition the listener\nto SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept\nqueue, and release the lock, all between the lockless read and the\ndelayed lock acquisition:\n\n  smc_listen_work (smc_hs_wq)          smc_close_active()\n  -------------------------------      -------------------------\n  release_sock(child)\n  if (sk_state == SMC_LISTEN) TRUE\n                                        lock_sock(listener)\n                                        sk_state = SMC_CLOSED\n                                        smc_close_cleanup_listen()\n                                        release_sock(listener)\n                                        flush_work(tcp_listen_work)\n  lock_sock_nested(listener)\n  smc_accept_enqueue(listener, child) /* child enqueued on dead listener */\n\nsmc_close_active() flushes only tcp_listen_work. Work items already\ndispatched onto smc_hs_wq for the CLC handshake continue running\nunguarded. smc_accept_enqueue() takes a sock_hold() on the child that\nis never released, so the child smc_sock, its clcsock, and the\nreference all leak. A remote peer that opens TCP connections while the\nserver calls close() can exhaust kernel memory.\n\nMove lock_sock_nested() to before the sk_state check so that the test\nand the enqueue are atomic under the listener lock."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"53c7938d8bcfde3296ec1a347ba2a9393c1fdcfa","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"feb71634bb1abab3e8fb5cde874b27001cc1282e","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"01865e1ddb126b25ac9eba5cdd7ec49e11183a64","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"00f89433777236ced4771211047fb5d4cd581cea","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"78e5ebcd1c10ed7c8bda0a99e0abd5b62da86d67","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"ff5bcd804b5bc5c64736b7d318c20e12ea9506b8","versionType":"git"},{"version":"fd57770dd198f5b2ddd5b9e6bf282cf98d63adb9","status":"affected","lessThan":"185a4caeecabc150106deda1da170b09f2ad803f","versionType":"git"},{"version":"d1d004585b40c212b338fc8a40cbaaf230ea4703","status":"affected","versionType":"git"},{"version":"4.19.299","status":"affected","lessThan":"4.20","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/af_smc.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.1","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.152","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/af_smc.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/53c7938d8bcfde3296ec1a347ba2a9393c1fdcfa"},{"url":"https://git.kernel.org/stable/c/feb71634bb1abab3e8fb5cde874b27001cc1282e"},{"url":"https://git.kernel.org/stable/c/01865e1ddb126b25ac9eba5cdd7ec49e11183a64"},{"url":"https://git.kernel.org/stable/c/00f89433777236ced4771211047fb5d4cd581cea"},{"url":"https://git.kernel.org/stable/c/78e5ebcd1c10ed7c8bda0a99e0abd5b62da86d67"},{"url":"https://git.kernel.org/stable/c/ff5bcd804b5bc5c64736b7d318c20e12ea9506b8"},{"url":"https://git.kernel.org/stable/c/185a4caeecabc150106deda1da170b09f2ad803f"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The bug fires when smc_listen_work() on smc_hs_wq finishes an inbound SMC/TCP handshake queued by smc_tcp_listen_work() for each remote connection to an AF_SMC listener, so any network peer that reaches the listener port drives the full path via SYN and CLC messages.\nAC:L - The attacker controls handshake completions by flooding SMC-capable TCP connections and overlapping them with listener close(), either by timing floods against restarts or locally by running server and client together; smc_close_active() only flushes tcp_listen_work, leaving smc_hs_wq workers racing through the unlocked sk_state check.\nPR:N - SMC performs no authentication; smc_create() and smc_listen() enforce no capabilities, and smc_listen_work() processes the CLC handshake immediately after TCP accept before any credential verification, so an unauthenticated remote peer need only reach the listener port.\nUI:N - Exploitation requires only inbound network connections and kernel handshake/close processing; no end-user action such as opening a file or mounting a filesystem is needed, and listener shutdown during deployments or restarts is routine automated server behavior.\nS:U - The leak accumulates orphaned smc_sock structures and clcsock references within the kernel networking subsystem on the targeted host; it does not cross VM, container, IOMMU, or other security boundaries.\nC:N - The bug is an unreleased sock_hold() leaving child sockets on a closed listener accept queue; objects are never freed prematurely, so there is no out-of-bounds read, use-after-free dereference, or kernel data disclosure to the attacker.\nI:N - Only reference counts are incremented without matching decrements; no memory is written out of bounds, no freed object is reused, and no control-flow or integrity primitive is obtained—only unreclaimable kernel allocations accumulate.\nA:H - Each successful race permanently leaks a child smc_sock, its clcsock, and sock references that smc_close_cleanup_listen() can never drain; a remote peer repeating handshakes during listener close can exhaust kernel memory and cause system-wide denial of service."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-25T05:41:37.608Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"5.15.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"6.6.152"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"6.12.104"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"6.18.45"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"7.1.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.1","versionEndExcluding":"7.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.19.299"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-74692","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T19:14:39.954097Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:16:09.513Z"}}]}}}