{"id":"CVE-2026-72317","title":"SUNRPC: pin upper rpc_clnt across the TLS connect_worker","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: pin upper rpc_clnt across the TLS connect_worker\n\nThe TLS connect path has a use-after-free: nothing pins the\nupper rpc_clnt across the delayed connect_worker. …","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < 79cd550f8c884523b604fbfa43eb02def74d6224","Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < 7a65b41b657b71d5a77861f47dd13eb4bc8e10d0","Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < 5b0427ba582d143a364301f825f4e32272f06d2d","Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < d49f6d098ed48775b9d27a9f9c5c220fdf76f102","Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < 46bc86c833956219bbfd246c1ffd832a479c5199","Linux 6.5"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"total","timestamp":"2026-10-16T18:46:35.255796Z"},"published":"2026-08-15","updated":"2026-10-16","sourceUpdated":"2026-10-16T18:55:17.145Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-72317","references":[{"url":"https://git.kernel.org/stable/c/79cd550f8c884523b604fbfa43eb02def74d6224"},{"url":"https://git.kernel.org/stable/c/7a65b41b657b71d5a77861f47dd13eb4bc8e10d0"},{"url":"https://git.kernel.org/stable/c/5b0427ba582d143a364301f825f4e32272f06d2d"},{"url":"https://git.kernel.org/stable/c/d49f6d098ed48775b9d27a9f9c5c220fdf76f102"},{"url":"https://git.kernel.org/stable/c/46bc86c833956219bbfd246c1ffd832a479c5199"}],"tags":["cve.org"],"epss":0.00644,"epssPercentile":0.49829,"ingestedAt":"2026-10-16T19:46:24.408Z","slug":"CVE-2026-72317","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: pin upper rpc_clnt across the TLS connect_worker\n\nThe TLS connect path has a use-after-free: nothing pins the\nupper rpc_clnt across the delayed connect_worker. xs_connect()\nstores task->tk_client in sock_xprt::clnt as a raw pointer\nand queues the worker; for TLS-secured transports that worker\nis xs_tcp_tls_setup_socket(), which reads several fields out\nof the saved pointer (cl_timeout, cl_program, cl_prog,\ncl_vers, cl_cred, cl_stats) to construct the args for the\ninner handshake rpc_clnt.\n\nThe xprt does not reference the rpc_clnt; the rpc_clnt\nreferences the xprt. xs_destroy() does cancel the\nconnect_worker, but it runs only when the xprt's refcount\ndrops to zero, which cannot happen until the rpc_clnt\nreleases its cl_xprt reference in rpc_free_client_work().\nWhen a TLS handshake fails fatally (for example, an mTLS\nmount whose client cert does not match the server), the\nconnecting task is woken with -EACCES and exits, the mount\ncaller invokes rpc_shutdown_client(), and the upper rpc_clnt\nis freed before the queued connect_worker fires.\nxs_tcp_tls_setup_socket() then dereferences the freed clnt,\nproducing the refcount_t underflow Michael Nemanov reported.\n\nTake a reference on the upper rpc_clnt in xs_connect() for\nTLS transports via a new rpc_hold_client() helper, and drop\nit in the connect_worker's exit path with rpc_release_client().\nThe xprt_lock_connect() / xprt_unlock_connect() pairing\nalready serialises xs_connect() with xs_tcp_tls_setup_socket(),\nso the take and release are balanced one-for-one.\n\nThe non-TLS connect worker (xs_tcp_setup_socket) never reads\nsock_xprt::clnt, so leave that path alone and avoid the\nclnt-holds-xprt-holds-clnt cycle that would otherwise prevent\nxprt destruction.\n\n## Affected\n\n- `Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < 79cd550f8c884523b604fbfa43eb02def74d6224`\n- `Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < 7a65b41b657b71d5a77861f47dd13eb4bc8e10d0`\n- `Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < 5b0427ba582d143a364301f825f4e32272f06d2d`\n- `Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < d49f6d098ed48775b9d27a9f9c5c220fdf76f102`\n- `Linux >= 75eb6af7acdf566c68d61e98e67ee2f235201c02 < 46bc86c833956219bbfd246c1ffd832a479c5199`\n- `Linux 6.5`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}