{"id":"CVE-2026-31446","revision":"03f5e913fc8848579737cff4a1952726","records":[{"revision":"03f5e913fc8848579737cff4a1952726","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-31446","aliases":[],"title":"ext4: fix use-after-free in update_super_work when racing with umount","description":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix use-after-free in update_super_work when racing with umount\n\nCommit b98535d09179 (\"ext4: fix bug_on in start_this_handle during umount\nfilesystem\") moved ext4_unregister_sysfs() before flushing s_sb_upd_work\nto prevent new error work from being queued via /proc/fs/ext4/xx/mb_groups\nreads during unmount. However, this introduced a use-after-free because\nupdate_super_work calls ext4_notify_error_sysfs() -> sysfs_notify() which\naccesses the kobject's kernfs_node after it has been freed by kobject_del()\nin ext4_unregister_sysfs():\n\n  update_super_work                ext4_put_super\n  -----------------                --------------\n                                   ext4_unregister_sysfs(sb)\n                                     kobject_del(&sbi->s_kobj)\n                                       __kobject_del()\n                                         sysfs_remove_dir()\n                                           kobj->sd = NULL\n                                         sysfs_put(sd)\n                                           kernfs_put()  // RCU free\n  ext4_notify_error_sysfs(sbi)\n    sysfs_notify(&sbi->s_kobj)\n      kn = kobj->sd              // stale pointer\n      kernfs_get(kn)             // UAF on freed kernfs_node\n                                   ext4_journal_destroy()\n                                     flush_work(&sbi->s_sb_upd_work)\n\nInstead of reordering the teardown sequence, fix this by making\next4_notify_error_sysfs() detect that sysfs has already been torn down\nby checking s_kobj.state_in_sysfs, and skipping the sysfs_notify() call\nin that case. A dedicated mutex (s_error_notify_mutex) serializes\next4_notify_error_sysfs() against kobject_del() in ext4_unregister_sysfs()\nto prevent TOCTOU races where the kobject could be deleted between the\nstate_in_sysfs check and the sysfs_notify() call.","state":0,"publishedAt":"2026-04-22T13:53:42.751+00:00","modifiedAt":"2026-10-19T18:35:48.381+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/ext4/ext4.h\",\n                        \"fs/ext4/super.c\",\n                        \"fs/ext4/sysfs.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"52c3a04f9ec2a16a4204d6274db338cb8d5b2d74\",\n                            \"lessThan\": \"c8fe17a1b308c3d8c703ebfb049b325f844342c3\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b98535d091795a79336f520b0708457aacf55c67\",\n                            \"lessThan\": \"c4d829737329f2290dd41e290b7d75effdb2a7ff\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b98535d091795a79336f520b0708457aacf55c67\",\n                            \"lessThan\": \"9449f99ba04f5dd1c8423ad8a90b3651d7240d1d\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b98535d091795a79336f520b0708457aacf55c67\",\n                            \"lessThan\": \"034053378dd81837fd6c7a43b37ee2e58d4f0b4e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b98535d091795a79336f520b0708457aacf55c67\",\n                            \"lessThan\": \"c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b98535d091795a79336f520b0708457aacf55c67\",\n                            \"lessThan\": \"08b10e6f37fc533a759e9833af0692242e8b3f93\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"b98535d091795a79336f520b0708457aacf55c67\",\n                            \"lessThan\": \"d15e4b0a418537aafa56b2cb80d44add83e83697\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"585ef03c9e79672781f954daae730dfe24bf3a46\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"afe490e48d47df1b3f64012835c1bc2f075a8c8b\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"5.15.38\",\n                            \"lessThan\": \"5.15.203\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.114\",\n                            \"lessThan\": \"5.11\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.17.6\",\n                            \"lessThan\": \"5.18\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"fs/ext4/ext4.h\",\n                        \"fs/ext4/super.c\",\n                        \"fs/ext4/sysfs.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"5.18\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.18\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.203\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.168\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.131\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.80\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.21\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.19.11\",\n                            \"lessThanOrEqual\": \"6.19.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.0\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/c8fe17a1b308c3d8c703ebfb049b325f844342c3","https://git.kernel.org/stable/c/c4d829737329f2290dd41e290b7d75effdb2a7ff","https://git.kernel.org/stable/c/9449f99ba04f5dd1c8423ad8a90b3651d7240d1d","https://git.kernel.org/stable/c/034053378dd81837fd6c7a43b37ee2e58d4f0b4e","https://git.kernel.org/stable/c/c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe","https://git.kernel.org/stable/c/08b10e6f37fc533a759e9833af0692242e8b3f93","https://git.kernel.org/stable/c/d15e4b0a418537aafa56b2cb80d44add83e83697"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-31446","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-31446","identifiers":["CVE-2026-31446"]},"retained":false,"historicalAffected":[]}],"coverage":[]}