# CVE-2026-39402: LXC authorization bypass in lxc-user-nic NIC deletion

Source: https://junglewise.ai/threats/cve-2026-39402-lxc-authorization-bypass-in-lxc-user-nic-nic-deletion  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-05. Updated: 2026-07-25  
License: CC BY 4.0 with a link back

CVE-2026-39402 · Severity: medium · CVSS 6.5 · Published 2026-05-05

LXC is a popular tool used to run multiple isolated Linux systems (containers) on a single host. A security flaw in one of its networking components allows a user on a shared server to disconnect the network interfaces of containers belonging to other users. This can lead to a denial-of-service where one tenant can disrupt the operations and connectivity of another tenant's applications.

Vendors: [Linuxcontainers](https://junglewise.ai/threats/vendors/linuxcontainers).

## Quick answers

**Is CVE-2026-39402 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-39402 being exploited in the wild.

**How severe is CVE-2026-39402?** Medium severity, with a CVSS score of 6.5, published 5 May 2026.

**Which products and versions are affected?** lxc lxc < 7.0.0.

**Is there a fix for CVE-2026-39402?** 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-2026-39402 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-39402?** Check whether you run Linuxcontainers Lxc. 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

A logic flaw exists in the find_line() function within the lxc-user-nic setuid helper. When processing the NIC database to authorize a deletion request, the function performs an interface name comparison after a 'goto next' label. This allows the authorization flag to be set based solely on a name match, even if previous checks for ownership, type, or link fields failed or were skipped. Consequently, an unprivileged attacker with a valid lxc-usernet policy entry can trigger the deletion of another user's OVS-attached network interface on the same bridge. This vulnerability is specific to multi-tenant environments using OpenVSwitch bridges and is addressed in version 7.0.0.

## Affected products

- lxc lxc < 7.0.0

## Timeline

- 2026-04-29: advisory: Vendor advisory published on GitHub
- 2026-05-05: disclosed: CVE published to NVD

## References

- [https://github.com/lxc/lxc/security/advisories/GHSA-3m9j-g9gc-vcvq](https://github.com/lxc/lxc/security/advisories/GHSA-3m9j-g9gc-vcvq)