{"id":"CVE-2026-31446","title":"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…","summary":"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…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cwe":["CWE-416"],"vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 5.10.114, < 5.11","linux_kernel >= 5.15.38, < 5.15.203","linux_kernel >= 5.17.6, < 5.18","linux_kernel >= 5.18.1, < 6.1.168","linux_kernel >= 6.2, < 6.6.131","linux_kernel >= 6.7, < 6.12.80","linux_kernel >= 6.13, < 6.18.21","linux_kernel >= 6.19, < 6.19.11","linux_kernel = 5.18","linux_kernel = 7.0"],"patched":["linux_kernel 6.19.11"],"published":"2026-04-22","updated":"2026-10-15","sourceUpdated":"2026-10-15T02:19:05.747","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-31446","references":[{"url":"https://git.kernel.org/stable/c/034053378dd81837fd6c7a43b37ee2e58d4f0b4e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/08b10e6f37fc533a759e9833af0692242e8b3f93","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9449f99ba04f5dd1c8423ad8a90b3651d7240d1d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c4d829737329f2290dd41e290b7d75effdb2a7ff","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c8fe17a1b308c3d8c703ebfb049b325f844342c3","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d15e4b0a418537aafa56b2cb80d44add83e83697","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00139,"epssPercentile":0.03246,"ingestedAt":"2026-09-08T15:33:26.990Z","ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:09:20.883316Z"},"slug":"CVE-2026-31446","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `linux_kernel >= 5.10.114, < 5.11`\n- `linux_kernel >= 5.15.38, < 5.15.203`\n- `linux_kernel >= 5.17.6, < 5.18`\n- `linux_kernel >= 5.18.1, < 6.1.168`\n- `linux_kernel >= 6.2, < 6.6.131`\n- `linux_kernel >= 6.7, < 6.12.80`\n- `linux_kernel >= 6.13, < 6.18.21`\n- `linux_kernel >= 6.19, < 6.19.11`\n- `linux_kernel = 5.18`\n- `linux_kernel = 7.0`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 6.19.11`","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}