# CVE-2026-84042: Crun: crun: rootful krun with passt executes container payload as host root

> Attackers can execute container payloads with host root privileges when using crun with libkrun and passt networking, requiring immediate upgrade.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/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:** 10 Sep 2026
- **Updated:** 15 Sep 2026
- **Also known as:** BELL-CVE-2026-84042, GHSA-ggww-wrxv-mmw2, UBUNTU-CVE-2026-84042

## What is CVE-2026-84042?

CVE-2026-84042 is a high-severity vulnerability in Red Hat Enterprise Linux 10, published on 10 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A flaw was found in crun. When crun is built with libkrun and a container is started rootful with passt networking (krun.use_passt), crun can execute attacker-controlled payload from the container image with host root privileges. The issue is a regression in crun 1.29. It affects crun >= 1.29

Weakness: CWE-269 (Improper Privilege Management)

## Which versions are affected by CVE-2026-84042?


## How do I fix CVE-2026-84042?

Upgrade to a fixed version.

## Is CVE-2026-84042 being exploited?

There is no known exploitation of CVE-2026-84042 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84042 and fix it if it is affected.

What it is: CVE-2026-84042 is a high-severity vulnerability in Red Hat Enterprise Linux 10, published on 10 Sep 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-2026-84042 in the wild and no public exploit code.

Affected product: Red Hat Enterprise Linux 10. 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-2026-84042/ (Markdown: https://insights.sbomify.com/CVE-2026-84042/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84042
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84042
- OSV: https://osv.dev/vulnerability/CVE-2026-84042

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84042/
Summaries are generated and may contain mistakes; the official description above is the record.