{"id":"CVE-2026-72317","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-72317","summary":"SUNRPC: pin upper rpc_clnt across the TLS connect_worker","details":"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. 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.","published":"2026-08-15T05:55:31.022Z","modified":"2026-08-16T03:48:40.049778562Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.6.145"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/46bc86c833956219bbfd246c1ffd832a479c5199"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5b0427ba582d143a364301f825f4e32272f06d2d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/79cd550f8c884523b604fbfa43eb02def74d6224"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7a65b41b657b71d5a77861f47dd13eb4bc8e10d0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d49f6d098ed48775b9d27a9f9c5c220fdf76f102"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/72xxx/CVE-2026-72317.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72317"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-16T03:48:40.049778562Z"}}