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.
Metrics
Affected Vendors & Products
References
History
Tue, 05 May 2026 21:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | lxc lxc-user-nic insufficient ownership validation allows cross-tenant OVS port deletion | |
| Weaknesses | CWE-863 | |
| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-05-05T20:45:24.107Z
Reserved: 2026-04-06T22:06:40.517Z
Link: CVE-2026-39402
No data.
Status : Received
Published: 2026-05-05T21:16:22.537
Modified: 2026-05-05T21:16:22.537
Link: CVE-2026-39402
No data.
OpenCVE Enrichment
Updated: 2026-05-05T22:30:33Z