CVE-2026-72431 alloc_tag: fix use-after-free in /proc/allocinfo after module unload
A use-after-free in the Linux kernel's allocinfo interface allows local attackers to execute code or escalate privileges after module unload.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72431?
CVE-2026-72431 is an use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
alloc_tag: fix use-after-free in /proc/allocinfo after module unload
allocinfo_start() only reinitializes the codetag iterator at position 0. For subsequent reads (position > 0), it reuses cached iterator state from the previous batch. allocinfo_stop() drops mod_lock between read batches, which allows module unload to complete and free the module memory that the cached iterator still references:
CPU0 (read) CPU1 (rmmod) ---- ---- allocinfo_start(pos=0) down_read(mod_lock) allocinfo_show() ... allocinfo_stop() up_read(mod_lock) codetag_unload_module() kfree(cmod) release_module_tags() ... free_mod_mem() allocinfo_start(pos=N) down_read(mod_lock) // reuses cached iter, skips re-init allocinfo_show() ct->filename <-- UAF
After free_mod_mem() frees the module's .rodata, allocinfo_show() dereferences ct->filename, ct->function which point there.
Save the iterator state in allocinfo_next() and resume from it in allocinfo_start() with codetag_next_ct(), which detects module removal via idr_find() returning NULL and skips to the next module.
Which versions are affected by CVE-2026-72431?
How do I fix CVE-2026-72431?
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-2026-72431 being exploited?
There is no known exploitation of CVE-2026-72431 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72431, DEBIAN-CVE-2026-72431, GHSA-pcf6-jjpm-2jrr, UBUNTU-CVE-2026-72431.