CVE-2026-80758 futex: Avoid private hash use-after-free on final put
A use-after-free in the Linux kernel futex subsystem allows local attackers to cause denial of service or potentially escalate privileges.
- 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-2026-80758?
CVE-2026-80758 is an use after free vulnerability in Linux, published on 4 Sep 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:
futex: Avoid private hash use-after-free on final put
futex_private_hash_put() drops the reference to fph before evaluating fph->mm for wake_up_var(). futex_ref_put() enables preemption again before returning. If that put drops the final reference and the task is preempted, another task can pivot to the replacement hash and free the old hash after an RCU grace period. The first task then reads fph->mm from the freed allocation when it resumes.
KASAN reports a slab-use-after-free in futex_private_hash_put(), with the read at offset 24 in a freed kmalloc-512 allocation. The allocation and free stacks point to futex_hash_allocate() and the RCU free path, respectively.
Load the mm pointer while the fph reference is still held and pass the saved value to wake_up_var(). wake_up_var() uses the pointer as a waitqueue key and does not dereference the mm through it.
Which versions are affected by CVE-2026-80758?
How do I fix CVE-2026-80758?
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-2026-80758 being exploited?
There is no known exploitation of CVE-2026-80758 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-80758, DEBIAN-CVE-2026-80758, GHSA-gw9j-5g8h-92qv, UBUNTU-CVE-2026-80758.