CVE-2026-89643 audit: avoid dropping live tree ref on fsnotify rule autoremove
A use-after-free vulnerability in the Linux kernel audit subsystem allows attackers to cause denial of service or potentially execute code via fsnotify rule autoremove.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89643?
CVE-2026-89643 is a critical use after free vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
audit: avoid dropping live tree ref on fsnotify rule autoremove
audit_del_rule() is used for both netlink deletion templates and internal fsnotify autoremove. The former passes a parsed template which owns a temporary tree reference; the latter passes the installed entry itself.
The unconditional audit_put_tree() at the end of audit_del_rule() assumes the template case. For mixed AUDIT_DIR plus AUDIT_EXE rules, an fsnotify autoremove event therefore drops the installed rule's live tree reference. Repeating this across rules sharing the same tree can free the tree while another rule still references it, and a later autoremove dereferences the freed pathname while comparing rules.
Move the temporary-tree put to audit_rule_change(), the caller that owns deletion templates. Keep it in the AUDIT_DEL_RULE cleanup so both successful deletion and -ENOENT still release the parser-owned tree.
[PM: dropped unnecessary comment for line length reasons]
Which versions are affected by CVE-2026-89643?
How do I fix CVE-2026-89643?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-89643 being exploited?
There is no known exploitation of CVE-2026-89643 in the wild and no public exploit code.
Sources
Also known as AZL-100316, BELL-CVE-2026-89643, DEBIAN-CVE-2026-89643, GHSA-qh9h-fg7c-vgxw, UBUNTU-CVE-2026-89643.