CVE-2026-31446
Description
In the Linux kernel, the following vulnerability has been resolved: ext4: fix use-after-free in update_super_work when racing with umount Commit b98535d09179 ("ext4: fix bug_on in start_this_handle during umount filesystem") moved ext4_unregister_sysfs() before flushing s_sb_upd_work to prevent new error work from being queued via /proc/fs/ext4/xx/mb_groups reads during unmount. However, this introduced a use-after-free because update_super_work calls ext4_notify_error_sysfs() -> sysfs_notify() which accesses the kobject's kernfs_node after it has been freed by kobject_del() in ext4_unregister_sysfs(): update_super_work ext4_put_super ----------------- -------------- ext4_unregister_sysfs(sb) kobject_del(&sbi->s_kobj) __kobject_del() sysfs_remove_dir() kobj->sd = NULL sysfs_put(sd) kernfs_put() // RCU free ext4_notify_error_sysfs(sbi) sysfs_notify(&sbi->s_kobj) kn = kobj->sd // stale pointer kernfs_get(kn) // UAF on freed kernfs_node ext4_journal_destroy() flush_work(&sbi->s_sb_upd_work) Instead of reordering the teardown sequence, fix this by making ext4_notify_error_sysfs() detect that sysfs has already been torn down by checking s_kobj.state_in_sysfs, and skipping the sysfs_notify() call in that case. A dedicated mutex (s_error_notify_mutex) serializes ext4_notify_error_sysfs() against kobject_del() in ext4_unregister_sysfs() to prevent TOCTOU races where the kobject could be deleted between the state_in_sysfs check and the sysfs_notify() call.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
| OS | Version | Status | Fixed in |
|---|---|---|---|
| sles | affected | | |
| debian | bookworm | fixed | 6.1.170-1 |
| debian | forky | fixed | 6.19.11-1 |
| debian | sid | fixed | 6.19.11-1 |
| debian | trixie | fixed | 6.12.85-1 |
| debian | bullseye | fixed | 6.1.170-1~deb11u1 |
| linux-kernel | affected | 5.11 | |
| linux-kernel | 5.18 | affected | |
| linux-kernel | 7.0 | affected | |
Application impact
| Vendor | Product | Versions | Fixed |
|---|---|---|---|
| gcp | | |
References
- https://git.kernel.org/stable/c/034053378dd81837fd6c7a43b37ee2e58d4f0b4e
- https://git.kernel.org/stable/c/08b10e6f37fc533a759e9833af0692242e8b3f93
- https://git.kernel.org/stable/c/9449f99ba04f5dd1c8423ad8a90b3651d7240d1d
- https://git.kernel.org/stable/c/c4d829737329f2290dd41e290b7d75effdb2a7ff
- https://git.kernel.org/stable/c/c8fe17a1b308c3d8c703ebfb049b325f844342c3
- https://git.kernel.org/stable/c/c97e282f7bfd0c3554c63d289964a5ca6a1d2ffe
- https://git.kernel.org/stable/c/d15e4b0a418537aafa56b2cb80d44add83e83697
- https://www.suse.com/security/cve/CVE-2026-31446.html
- https://security-tracker.debian.org/tracker/CVE-2026-31446
CWEs
CWE-416
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.