Executive brief
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.
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