{"cve":"CVE-2026-72317","nvd":{"published":"2026-08-15T06:22:04.620","modified":"2026-10-16T19:17:22.153","status":"Received","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8},"cwes":[],"references":["https://git.kernel.org/stable/c/46bc86c833956219bbfd246c1ffd832a479c5199","https://git.kernel.org/stable/c/5b0427ba582d143a364301f825f4e32272f06d2d","https://git.kernel.org/stable/c/79cd550f8c884523b604fbfa43eb02def74d6224","https://git.kernel.org/stable/c/7a65b41b657b71d5a77861f47dd13eb4bc8e10d0","https://git.kernel.org/stable/c/d49f6d098ed48775b9d27a9f9c5c220fdf76f102"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:48:17.459049833+00:00"},"epss":{"cve":"CVE-2026-72317","score":0.00644,"percentile":0.50599,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}