CVE-2026-99179 watch_queue: Fix note pool publication race in watch_queue_set_size()
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99179?
CVE-2026-99179 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
watch_queue: Fix note pool publication race in watch_queue_set_size()
There is a race between watch_queue_set_size() and post_one_notification(). watch_queue_set_size() publishes wqueue->notes, notes_bitmap, nr_pages and nr_notes with plain stores, and post_one_notification() reads them with plain loads under a different lock, so nothing orders the four stores against the poster's loads: depending on the build, notes can be stored last (gcc 14 on x86-64 does this). Since keyctl_watch_key() lets a watch attach to a queue before it is sized, post_one_notification() can already be running on another CPU at that moment: it reads nr_notes > 0, passes its bounds check, and then reads notes while it is still NULL, dereferencing notes[0].
An unprivileged user triggers this reliably by watching one of its own keys through a notification pipe and racing ioctl(IOC_WATCH_QUEUE_SET_SIZE) on that pipe against keyctl(KEYCTL_SETPERM) on the key from another CPU, triggering:
BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: 0010:post_one_notification.isra.0+0xa2/0x1e0 Call Trace: __post_watch_notification+0x148/0x180 keyctl_setperm_key+0x119/0x130 do_syscall_64+0x108/0x4c0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Kernel panic - not syncing: Fatal exception in interrupt
Fix this by publishing nr_notes last with smp_store_release(), and by reading it once with smp_load_acquire() in post_one_notification() before the bitmap and the page array are touched. A poster that observes a non-zero nr_notes then also observes the pool behind it; one that observes zero drops the notification as before.
Which versions are affected by CVE-2026-99179?
How do I fix CVE-2026-99179?
Upgrade to a fixed version.
Is CVE-2026-99179 being exploited?
There is no known exploitation of CVE-2026-99179 in the wild and no public exploit code.
Sources
Also known as AZL-111338, BELL-CVE-2026-99179, DEBIAN-CVE-2026-99179, GHSA-6fpx-qf4r-r7v5, UBUNTU-CVE-2026-99179.