# CVE-2026-84042: crun privilege escalation in libkrun with passt networking

Source: https://junglewise.ai/threats/cve-2026-84042-crun-privilege-escalation-in-libkrun-with-passt-networking  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-10. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-84042 · Severity: high · CVSS 7.8 · Published 2026-09-10

crun is a container runtime that can execute containers on Linux systems. When built with libkrun support and configured to use passt networking, a vulnerability allows an attacker to execute malicious code from a container image with root privileges on the host system, bypassing normal container isolation. This affects rootful (root-privileged) containers and can lead to complete host compromise.

Technologies: [Containers Crun](https://junglewise.ai/threats/technologies/crun). Vendors: [Containers](https://junglewise.ai/threats/vendors/containers).

## Quick answers

**Is CVE-2026-84042 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-84042 being exploited in the wild.

**How severe is CVE-2026-84042?** High severity, with a CVSS score of 7.8, published 10 September 2026.

**Which products and versions are affected?** Containers Crun >= 1.29.

**Is there a fix for CVE-2026-84042?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-84042 attacked?** It is attacked with local access.

**Am I affected by CVE-2026-84042?** Check whether you run Containers Crun at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an improper privilege management flaw (CWE-269) that occurs when crun is built with libkrun and a container is started in rootful mode with passt networking enabled (krun.use_passt). An attacker who controls the container image can execute arbitrary payloads with host root privileges, escaping normal container isolation boundaries. The attack requires low privileges and no user interaction but has high complexity requirements due to the specific build and runtime configuration needed. The issue is a regression introduced in crun 1.29 and affects all versions >= 1.29. Mitigation is to avoid running untrusted images with krun and passt networking until a patch is released.

## Affected products

- containers crun >= 1.29

## Timeline

- 2026-09-10: disclosed

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/security/cve/CVE-2026-84042](https://access.redhat.com/security/cve/CVE-2026-84042)

## Related threats

- [crun symlink following in /dev/null leads to host file access](https://junglewise.ai/threats/cve-2026-88265-crun-symlink-following-in-dev-null-leads-to-host-file-access)
- [crun terminal setup path redirection vulnerability](https://junglewise.ai/threats/cve-2026-88264-crun-terminal-setup-path-redirection-vulnerability)