# CVE-2026-39402: liblxc1: lxc is a Linux container runtime

CVE-2026-39402 is fixed in 8 products on 1 platform, first by liblxc-common 3.0.3-0ubuntu1~18.04.3+esm1, released May 5, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-39402
- Priority: Routine
- CVSS: 6.5 (Medium)
- EPSS: 0.0016
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 5, 2026

## Description

lxc is a Linux container runtime. In the setuid helper lxc-user-nic, the delete path contains a logic flaw in the find_line() function that allows an unprivileged user to delete OVS-attached network interfaces belonging to other users. When lxc-user-nic delete scans its NIC database to authorize a deletion request, the interface name comparison can set the authorization flag based on a name match alone, even when the ownership, type, and link fields in that database entry belong to a different user. The vulnerable check sits after the goto next label handling, meaning it is reachable on lines where earlier ownership checks failed or were skipped. Because nothing downstream of this authorization signal re-verifies that the matched database line actually belongs to the caller, an unprivileged attacker with a valid lxc-usernet policy entry can trigger deletion of another user's OVS port on the same bridge. This is limited to multi-tenant environments using lxc-user-nic with OpenVSwitch bridges. The impact is denial of service - one tenant can repeatedly disconnect networking from containers run by another tenant on shared infrastructure. This is patched in version 7.0.0.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | liblxc-common Ubuntu 18.04.6 LTS (bionic) | 3.0.3-0ubuntu1~18.04.3+esm1 | [liblxc-common 3.0.3-0ubuntu1~18.04.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-liblxc-common-3.0.3-0ubuntu1-18.04.3-esm1.md) | May 5, 2026 |
| Linux | liblxc-common Ubuntu 20.04 LTS (focal) | 1:4.0.12-0ubuntu1~20.04.1+esm1 | [liblxc-common 1:4.0.12-0ubuntu1~20.04.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-liblxc-common-1-4.0.12-0ubuntu1-20.04.1-esm1.md) | May 5, 2026 |
| Linux | liblxc-common Ubuntu 22.04.1 LTS (jammy) | 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1 | [liblxc-common 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-liblxc-common-1-5.0.0-git2209-g5a7b9ce67-0ubuntu1.1-esm1.md) | May 5, 2026 |
| Linux | liblxc-common Ubuntu 24.04.5 LTS (noble) | 1:5.0.3-2ubuntu7.3+esm1 | [liblxc-common 1:5.0.3-2ubuntu7.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-liblxc-common-1-5.0.3-2ubuntu7.3-esm1.md) | May 5, 2026 |
| Linux | liblxc-common Ubuntu 26.04.1 LTS (resolute) | 1:6.0.6-1ubuntu1+esm1 | [liblxc-common 1:6.0.6-1ubuntu1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-liblxc-common-1-6.0.6-1ubuntu1-esm1.md) | May 5, 2026 |
| Linux | liblxc1 Ubuntu 18.04.6 LTS (bionic) | 3.0.3-0ubuntu1~18.04.3+esm1 | [liblxc1 3.0.3-0ubuntu1~18.04.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-liblxc1-3.0.3-0ubuntu1-18.04.3-esm1.md) | May 5, 2026 |
| Linux | liblxc1 Ubuntu 20.04 LTS (focal) | 1:4.0.12-0ubuntu1~20.04.1+esm1 | [liblxc1 1:4.0.12-0ubuntu1~20.04.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-liblxc1-1-4.0.12-0ubuntu1-20.04.1-esm1.md) | May 5, 2026 |
| Linux | liblxc1 Ubuntu 22.04.1 LTS (jammy) | 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1 | [liblxc1 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-liblxc1-1-5.0.0-git2209-g5a7b9ce67-0ubuntu1.1-esm1.md) | May 5, 2026 |
| Linux | liblxc1t64 Ubuntu 24.04.5 LTS (noble) | 1:5.0.3-2ubuntu7.3+esm1 | [liblxc1t64 1:5.0.3-2ubuntu7.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-liblxc1t64-1-5.0.3-2ubuntu7.3-esm1.md) | May 5, 2026 |
| Linux | liblxc1t64 Ubuntu 26.04.1 LTS (resolute) | 1:6.0.6-1ubuntu1+esm1 | [liblxc1t64 1:6.0.6-1ubuntu1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-liblxc1t64-1-6.0.6-1ubuntu1-esm1.md) | May 5, 2026 |
| Linux | libpam-cgfs Ubuntu 18.04.6 LTS (bionic) | 3.0.3-0ubuntu1~18.04.3+esm1 | [libpam-cgfs 3.0.3-0ubuntu1~18.04.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libpam-cgfs-3.0.3-0ubuntu1-18.04.3-esm1.md) | May 5, 2026 |
| Linux | libpam-cgfs Ubuntu 20.04 LTS (focal) | 1:4.0.12-0ubuntu1~20.04.1+esm1 | [libpam-cgfs 1:4.0.12-0ubuntu1~20.04.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libpam-cgfs-1-4.0.12-0ubuntu1-20.04.1-esm1.md) | May 5, 2026 |
| Linux | libpam-cgfs Ubuntu 22.04.1 LTS (jammy) | 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1 | [libpam-cgfs 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libpam-cgfs-1-5.0.0-git2209-g5a7b9ce67-0ubuntu1.1-esm1.md) | May 5, 2026 |
| Linux | libpam-cgfs Ubuntu 24.04.5 LTS (noble) | 1:5.0.3-2ubuntu7.3+esm1 | [libpam-cgfs 1:5.0.3-2ubuntu7.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libpam-cgfs-1-5.0.3-2ubuntu7.3-esm1.md) | May 5, 2026 |
| Linux | libpam-cgfs Ubuntu 26.04.1 LTS (resolute) | 1:6.0.6-1ubuntu1+esm1 | [libpam-cgfs 1:6.0.6-1ubuntu1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libpam-cgfs-1-6.0.6-1ubuntu1-esm1.md) | May 5, 2026 |
| Linux | lxc Debian 12.15 (bookworm) | 1:5.0.2-1+deb12u4 | [DEBIAN-CVE-2026-39402](https://patchblox.com/security/data/fix/linux/debian-cve-2026-39402.md) | May 27, 2026 |
| Linux | lxc Debian 13.5 (trixie) | 1:6.0.4-4+deb13u3 | [DEBIAN-CVE-2026-39402](https://patchblox.com/security/data/fix/linux/debian-cve-2026-39402.md) | May 27, 2026 |
| Linux | lxc Debian 14 | 1:7.0.0-1 | [DEBIAN-CVE-2026-39402](https://patchblox.com/security/data/fix/linux/debian-cve-2026-39402.md) | May 27, 2026 |
| Linux | lxc Ubuntu 18.04.6 LTS (bionic) | 3.0.3-0ubuntu1~18.04.3+esm1 | [lxc 3.0.3-0ubuntu1~18.04.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-lxc-3.0.3-0ubuntu1-18.04.3-esm1.md) | May 5, 2026 |
| Linux | lxc Ubuntu 20.04 LTS (focal) | 1:4.0.12-0ubuntu1~20.04.1+esm1 | [lxc 1:4.0.12-0ubuntu1~20.04.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-lxc-1-4.0.12-0ubuntu1-20.04.1-esm1.md) | May 5, 2026 |
| Linux | lxc Ubuntu 22.04.1 LTS (jammy) | 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1 | [lxc 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-lxc-1-5.0.0-git2209-g5a7b9ce67-0ubuntu1.1-esm1.md) | May 5, 2026 |
| Linux | lxc Ubuntu 24.04.5 LTS (noble) | 1:5.0.3-2ubuntu7.3+esm1 | [lxc 1:5.0.3-2ubuntu7.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-lxc-1-5.0.3-2ubuntu7.3-esm1.md) | May 5, 2026 |
| Linux | lxc Ubuntu 26.04.1 LTS (resolute) | 1:6.0.6-1ubuntu1+esm1 | [lxc 1:6.0.6-1ubuntu1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-lxc-1-6.0.6-1ubuntu1-esm1.md) | May 5, 2026 |
| Linux | lxc-tests Ubuntu 24.04.5 LTS (noble) | 1:5.0.3-2ubuntu7.3+esm1 | [lxc-tests 1:5.0.3-2ubuntu7.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-lxc-tests-1-5.0.3-2ubuntu7.3-esm1.md) | May 5, 2026 |
| Linux | lxc-tests Ubuntu 26.04.1 LTS (resolute) | 1:6.0.6-1ubuntu1+esm1 | [lxc-tests 1:6.0.6-1ubuntu1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-lxc-tests-1-6.0.6-1ubuntu1-esm1.md) | May 5, 2026 |
| Linux | lxc-utils Ubuntu 18.04.6 LTS (bionic) | 3.0.3-0ubuntu1~18.04.3+esm1 | [lxc-utils 3.0.3-0ubuntu1~18.04.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-lxc-utils-3.0.3-0ubuntu1-18.04.3-esm1.md) | May 5, 2026 |
| Linux | lxc-utils Ubuntu 20.04 LTS (focal) | 1:4.0.12-0ubuntu1~20.04.1+esm1 | [lxc-utils 1:4.0.12-0ubuntu1~20.04.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-lxc-utils-1-4.0.12-0ubuntu1-20.04.1-esm1.md) | May 5, 2026 |
| Linux | lxc-utils Ubuntu 22.04.1 LTS (jammy) | 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1 | [lxc-utils 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-lxc-utils-1-5.0.0-git2209-g5a7b9ce67-0ubuntu1.1-esm1.md) | May 5, 2026 |
| Linux | lxc-utils Ubuntu 24.04.5 LTS (noble) | 1:5.0.3-2ubuntu7.3+esm1 | [lxc-utils 1:5.0.3-2ubuntu7.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-lxc-utils-1-5.0.3-2ubuntu7.3-esm1.md) | May 5, 2026 |
| Linux | lxc1 Ubuntu 18.04.6 LTS (bionic) | 3.0.3-0ubuntu1~18.04.3+esm1 | [lxc1 3.0.3-0ubuntu1~18.04.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-lxc1-3.0.3-0ubuntu1-18.04.3-esm1.md) | May 5, 2026 |
| Linux | lxc1 Ubuntu 20.04 LTS (focal) | 1:4.0.12-0ubuntu1~20.04.1+esm1 | [lxc1 1:4.0.12-0ubuntu1~20.04.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-lxc1-1-4.0.12-0ubuntu1-20.04.1-esm1.md) | May 5, 2026 |
| Linux | lxc1 Ubuntu 22.04.1 LTS (jammy) | 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1 | [lxc1 1:5.0.0~git2209-g5a7b9ce67-0ubuntu1.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-lxc1-1-5.0.0-git2209-g5a7b9ce67-0ubuntu1.1-esm1.md) | May 5, 2026 |
| Linux | lxc1 Ubuntu 24.04.5 LTS (noble) | 1:5.0.3-2ubuntu7.3+esm1 | [lxc1 1:5.0.3-2ubuntu7.3+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-lxc1-1-5.0.3-2ubuntu7.3-esm1.md) | May 5, 2026 |

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