# CVE-2026-43178: procfs: fix possible double mmput() in do_procmap_query()

> A double free vulnerability in the Linux kernel's procfs allows local attackers to cause a denial of service via crafted buffer sizes.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 May 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-43178, DEBIAN-CVE-2026-43178, GHSA-6xqc-j72q-x4c8, UBUNTU-CVE-2026-43178

## What is CVE-2026-43178?

CVE-2026-43178 is a high-severity memory corruption vulnerability in Linux kernel, published on 6 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-415 (Double Free), CWE-1341 (Multiple Releases of Same Resource or Handle)

## Which versions are affected by CVE-2026-43178?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43178?

Apply the vendor's patch.

## Is CVE-2026-43178 being exploited?

There is no known exploitation of CVE-2026-43178 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43178 and fix it if it is affected.

What it is: CVE-2026-43178 is a high-severity memory corruption vulnerability in Linux kernel, published on 6 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43178 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43178/ (Markdown: https://insights.sbomify.com/CVE-2026-43178/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43178
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43178
- OSV: https://osv.dev/vulnerability/CVE-2026-43178

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43178/
Summaries are generated and may contain mistakes; the official description above is the record.