# CVE-2026-76642: util-linux libmount Privilege Escalation via Failed Mount Helper

> Unprivileged users can escalate privileges by exploiting mount helper failures to modify filesystem permissions or inherit suid bits.

- **Severity:** High 8.5 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **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:** 3 Sep 2026
- **Updated:** 3 Sep 2026
- **Also known as:** ALPINE-CVE-2026-76642, AZL-99081, BELL-CVE-2026-76642, DEBIAN-CVE-2026-76642, ECHO-b20e-705a-6d36, GHSA-m25x-3hj9-m26f, OESA-2026-3722, OESA-2026-3723, ROOT-OS-DEBIAN-12-CVE-2026-76642, ROOT-OS-DEBIAN-13-CVE-2026-76642, UBUNTU-CVE-2026-76642

## What is CVE-2026-76642?

CVE-2026-76642 is a high-severity vulnerability in util-linux, published on 3 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

util-linux versions through 2.41.5 and 2.42.2 fail to check mount helper exit status before running post-mount hooks, allowing unprivileged users to execute privileged operations on pre-existing filesystems. Attackers can exploit X-mount.idmap or X-mount.owner hooks to clone filesystems with inherited suid bits or modify target inode permissions after a helper fails, achieving privilege escalation.

Weakness: CWE-390 (Detection of Error Condition Without Action)

## Which versions are affected by CVE-2026-76642?


## How do I fix CVE-2026-76642?

Apply the vendor's patch.

## Is CVE-2026-76642 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-76642 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76642 and fix it if it is affected.

What it is: CVE-2026-76642 is a high-severity vulnerability in util-linux, published on 3 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-76642 exists.

Affected product: util-linux. 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-2026-76642/ (Markdown: https://insights.sbomify.com/CVE-2026-76642/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76642
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76642
- OSV: https://osv.dev/vulnerability/CVE-2026-76642

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-76642/
Summaries are generated and may contain mistakes; the official description above is the record.