{"id":"CVE-2026-72221","state":"PUBLISHED","title":"sunrpc: wait for in-flight TLS handshake callback when cancel loses race","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsunrpc: wait for in-flight TLS handshake callback when cancel loses race\n\nWhen wait_for_completion_interruptible_timeout() in\nsvc_tcp_handshake() returns 0 (timeout) or -ERESTARTSYS (signal) and\ntls_handshake_cancel() then returns false, handshake_complete() has\nwon the cancellation race: it has set HANDSHAKE_F_REQ_COMPLETED and\nis about to invoke svc_tcp_handshake_done(), but the callback's\nside effects on xpt_flags and on svsk->sk_handshake_done have not\nyet committed.\n\nThe current code reads xpt_flags immediately to decide whether the\nsession succeeded. Two races result.\n\nIf the callback has executed set_bit(XPT_TLS_SESSION) but not yet\nclear_bit(XPT_HANDSHAKE), svc_tcp_handshake() sees a session,\nenqueues the transport, and returns. svc_xprt_received() then\nclears XPT_BUSY, a worker thread picks the transport up, the\ndispatcher in svc_handle_xprt() observes XPT_HANDSHAKE still set,\nand xpo_handshake is invoked a second time. That svc_tcp_handshake()\ncalls init_completion(&svsk->sk_handshake_done) while the original\ncallback concurrently calls complete_all() on it, corrupting the\nembedded swait_queue.\n\nIf the callback has set HANDSHAKE_F_REQ_COMPLETED but not yet\nentered svc_tcp_handshake_done(), svc_tcp_handshake() reads\nXPT_TLS_SESSION as clear and tears the connection down even though\nthe handshake is about to succeed.\n\nWait for the callback to commit before inspecting xpt_flags. The\ncompletion is guaranteed to fire because handshake_complete()\ninvokes svc_tcp_handshake_done() unconditionally once it has set\nHANDSHAKE_F_REQ_COMPLETED.","publishedAt":"2026-08-15T05:54:14.539Z","updatedAt":"2026-10-16T18:45:02.148Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/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":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"0d8ceb39884148dc7a2fdf71e1cac5961ed1d2b9","versionType":"git"},{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"e0f4691d42a54d359d8b64509fd9ab938d4f2a33","versionType":"git"},{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"65b23bec1fca6e9ebdc3e6041ebf8c6ab074141b","versionType":"git"},{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"a4f878e8ecd729ccf2e50993444e217583adeace","versionType":"git"},{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"d00e32f84ca1a77cb67a3fbf59f58dada95f5a21","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sunrpc/svcsock.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.4","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","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/sunrpc/svcsock.c"]}],"references":["https://git.kernel.org/stable/c/0d8ceb39884148dc7a2fdf71e1cac5961ed1d2b9","https://git.kernel.org/stable/c/e0f4691d42a54d359d8b64509fd9ab938d4f2a33","https://git.kernel.org/stable/c/65b23bec1fca6e9ebdc3e6041ebf8c6ab074141b","https://git.kernel.org/stable/c/a4f878e8ecd729ccf2e50993444e217583adeace","https://git.kernel.org/stable/c/d00e32f84ca1a77cb67a3fbf59f58dada95f5a21"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72221.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72221","state":"PUBLISHED","datePublished":"2026-08-15T05:54:14.539Z","dateUpdated":"2026-10-16T18:45:02.148Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.913Z"},"containers":{"cna":{"title":"sunrpc: wait for in-flight TLS handshake callback when cancel loses race","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsunrpc: wait for in-flight TLS handshake callback when cancel loses race\n\nWhen wait_for_completion_interruptible_timeout() in\nsvc_tcp_handshake() returns 0 (timeout) or -ERESTARTSYS (signal) and\ntls_handshake_cancel() then returns false, handshake_complete() has\nwon the cancellation race: it has set HANDSHAKE_F_REQ_COMPLETED and\nis about to invoke svc_tcp_handshake_done(), but the callback's\nside effects on xpt_flags and on svsk->sk_handshake_done have not\nyet committed.\n\nThe current code reads xpt_flags immediately to decide whether the\nsession succeeded. Two races result.\n\nIf the callback has executed set_bit(XPT_TLS_SESSION) but not yet\nclear_bit(XPT_HANDSHAKE), svc_tcp_handshake() sees a session,\nenqueues the transport, and returns. svc_xprt_received() then\nclears XPT_BUSY, a worker thread picks the transport up, the\ndispatcher in svc_handle_xprt() observes XPT_HANDSHAKE still set,\nand xpo_handshake is invoked a second time. That svc_tcp_handshake()\ncalls init_completion(&svsk->sk_handshake_done) while the original\ncallback concurrently calls complete_all() on it, corrupting the\nembedded swait_queue.\n\nIf the callback has set HANDSHAKE_F_REQ_COMPLETED but not yet\nentered svc_tcp_handshake_done(), svc_tcp_handshake() reads\nXPT_TLS_SESSION as clear and tears the connection down even though\nthe handshake is about to succeed.\n\nWait for the callback to commit before inspecting xpt_flags. The\ncompletion is guaranteed to fire because handshake_complete()\ninvokes svc_tcp_handshake_done() unconditionally once it has set\nHANDSHAKE_F_REQ_COMPLETED."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"0d8ceb39884148dc7a2fdf71e1cac5961ed1d2b9","versionType":"git"},{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"e0f4691d42a54d359d8b64509fd9ab938d4f2a33","versionType":"git"},{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"65b23bec1fca6e9ebdc3e6041ebf8c6ab074141b","versionType":"git"},{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"a4f878e8ecd729ccf2e50993444e217583adeace","versionType":"git"},{"version":"b3cbf98e2fdf3cb147a95161560cd25987284330","status":"affected","lessThan":"d00e32f84ca1a77cb67a3fbf59f58dada95f5a21","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/sunrpc/svcsock.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.4","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","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/sunrpc/svcsock.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/0d8ceb39884148dc7a2fdf71e1cac5961ed1d2b9"},{"url":"https://git.kernel.org/stable/c/e0f4691d42a54d359d8b64509fd9ab938d4f2a33"},{"url":"https://git.kernel.org/stable/c/65b23bec1fca6e9ebdc3e6041ebf8c6ab074141b"},{"url":"https://git.kernel.org/stable/c/a4f878e8ecd729ccf2e50993444e217583adeace"},{"url":"https://git.kernel.org/stable/c/d00e32f84ca1a77cb67a3fbf59f58dada95f5a21"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - Reachable over TCP by any remote peer of an in-kernel NFS/RPC server (nfsd) via the pre-auth RPC_AUTH_TLS NULL-procedure STARTTLS path that invokes svc_tcp_handshake() on the accepted SUNRPC transport.\nAC:L - The attacker controls both sides of the race by timing TLS client handshake messages against the fixed 5-second SVC_HANDSHAKE_TO and opening many parallel connections to reliably hit the cancel-lost window.\nPR:N - No credentials or export authorization are required; svcauth_tls_accept() accepts empty AUTH_TLS on RPC NULL from any TCP client, and svcauth_unix_set_client() skips IP export checks when rq_proc==0.\nUI:N - Exploitation requires only scripted network connections and TLS client traffic to nfsd; no victim user interaction such as mounting a filesystem or opening a file is needed.\nS:U - Memory corruption occurs in nfsd kernel worker context on the same host; impact is kernel privilege compromise within the server security authority, not a VM escape or IOMMU boundary bypass.\nC:H - A second svc_tcp_handshake() can call init_completion() while svc_tcp_handshake_done() concurrently calls complete_all(), corrupting the embedded swait_queue in heap-allocated svc_sock and enabling arbitrary kernel memory disclosure.\nI:H - Corrupting completion wait-queue metadata in the svc_sock heap object can be leveraged for arbitrary kernel writes and control-flow hijacking to achieve local privilege escalation on the NFS server.\nA:H - The swait_queue corruption can trigger kernel oops/panic, and the alternate race path tears down connections whose TLS handshake is about to succeed, enabling repeatable remote denial-of-service against nfsd."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:41:42.766Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-72221","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T18:43:57.343257Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T18:45:02.148Z"}}]}}}