{"id":"CVE-2026-90036","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-90036","summary":"NFSD: Prevent client use-after-free during blocked-lock reaping","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: Prevent client use-after-free during blocked-lock reaping\n\nA bare lock owner -- its only remaining reference a blocked lock on\nnn->blocked_locks_lru -- holds a raw pointer to its nfs4_client but\nno reference keeping the client alive. When the per-net laundromat\nreaps such a lock, freeing the nbl drops the owner reference\nheld through flc_owner, and the final nfs4_put_stateowner()\ntakes the client's cl_lock. Because the laundromat detaches the\nnbl first, __destroy_client() no longer finds it, so a concurrent\nforce_expire_client() can free the client before nfs4_put_stateowner()\nruns, dereferencing cl_lock in freed memory.\n\nPin the client with cl_rpc_users before dropping\nnn->blocked_locks_lock, and skip clients already expiring, whose\nblocked locks __destroy_client() frees while holding an owner\nreference. Take nn->client_lock outside nn->blocked_locks_lock.\nEvery other site holds nn->blocked_locks_lock as a leaf, acquiring\nno further lock, so placing nn->client_lock outside it cannot form\na lock-order cycle.","published":"2026-09-16T10:33:35.967Z","modified":"2026-09-17T03:47:27.500255050Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.18.51"}],"fix":null,"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6fedb2eaff77554ca7a0deffd2e8bc0d6e8b38b0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9026932ac8be4d0ae01db47f23619a98cc57b671"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cd489b03587378645fe0d20142a33f1ed60bac98"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90036.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90036"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-17T03:47:27.500255050Z"}}