CVE-2026-99169 futex: Fix mm reuse handling for FUT_OFF_MMSHARED
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99169?
CVE-2026-99169 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
futex: Fix mm reuse handling for FUT_OFF_MMSHARED
A FUT_OFF_MMSHARED futex is a shared futex that refers to an MM. It is possible for a process to wait on a shared futex with a different MM because a FUT_OFF_INODE waiter can be requeued onto a FUT_OFF_MMSHARED futex by another process. This can cause FUT_OFF_MMSHARED waiters on a freed MM to consume wakeups intended for a newly allocated MM at the same address.
Fix it by keying FUT_OFF_MMSHARED using a unique 64-bit per-MM ID. Leave private futexes as before to avoid influencing the performance of the hotpath.
(Multi-threaded processes typically implicitly use FUT_OFF_MMSHARED by setting clear_child_tid such that it points into anonymous memory, which causes mm_release() in a multi-threaded mm to perform FUTEX_WAKE.)
Which versions are affected by CVE-2026-99169?
How do I fix CVE-2026-99169?
Upgrade to a fixed version.
Is CVE-2026-99169 being exploited?
There is no known exploitation of CVE-2026-99169 in the wild and no public exploit code.
Sources
Also known as AZL-111317, BELL-CVE-2026-99169, DEBIAN-CVE-2026-99169, GHSA-8p9g-5mhx-rvh4, UBUNTU-CVE-2026-99169.