{"id":"CVE-2026-89712","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-89712","summary":"NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nNFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock\n\nnfsd4_ssc_expire_umount() walks nn->nfsd_ssc_mount_list with\nlist_for_each_entry_safe(ni, tmp, ...).  For each expired entry it\nsets nsui_busy = true, drops nfsd_ssc_lock to run mntput() on the\nsource vfsmount, then reacquires the lock to list_del + kfree the\nentry and continue iterating via the macro's saved tmp pointer.\n\nThe nsui_busy flag protects the current ni from concurrent\nnfsd4_ssc_setup_dul() finders during the lock-drop window, but it\ndoes not pin tmp.  Another nfsd RPC thread that fails its source-\nserver mount and reaches nfsd4_ssc_cancel_dul() will, during that\nsame window, take nfsd_ssc_lock, list_del + kfree its own ssc_umount\nitem, and release the lock.  If that item is the saved tmp of the\nexpire walk, the next iteration dereferences a freed\nnfsd4_ssc_umount_item.\n\nRestart the walk from the head after the mntput() unlock window so\nno saved next pointer survives the lock-drop.  The list is bounded\nby the number of active inter-server source mounts (typically small)\nand the expire delayed-work runs periodically rather than per-IO,\nso the restart is cheap.","published":"2026-09-11T19:46:27.018Z","modified":"2026-09-14T03:46:27.262842334Z","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":"6.12.109"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/036c1b182f4da65363e79ec0ac276edc6b7296e5"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4ed8d2317aef21cc2a9e5a55d6b59860b4b151a8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7377fa964b8aaf47cb04e5efcc4c82d15e8c2ce9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/77de363d9a1c8cd35f20482782c612cda085791a"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89712.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89712"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-14T03:46:27.262842334Z"}}