LXC CVE-2026-100395

Requires local, attacker-controlled contents in a source container's root filesystem (specifically the file lxc-copy rewrites when updating the hostname during a clone) so a symlink can be planted there, AND a host administrator must subsequently run lxc-copy against that container so the root-privileged host-context write follows the symlink. Limiting factors: not remotely reachable, depends on the privileged copy operation being performed on an attacker-influenced container, and requires prior access to that container's filesystem - this is a privilege-escalation/container-escape primitive, not a default-configuration remote exploit. Exact affected/fixed LXC versions are not stated in the available data.

No CVSS vector, EPSS, KEV, SSVC, or POC data is provided - every risk signal below is INFERRED from the terse description ('lxc-copy host-context hostname update follows symlink') and the reporter (vendor:ubuntu, which maintains LXC/LXD/Incus). The pattern describes a classic symlink-following flaw (CWE-59/TOCTOU class): lxc-copy runs with root privileges on the HOST and, while cloning a container, updates the hostname by writing into a path within the (attacker-influenceable) container rootfs; if it follows a symlink placed there, a privileged host-context write is redirected to an arbitrary host file. That is a container-to-host boundary crossing (scope change) with root-level arbitrary write - inherently high impact IF reachable. However, real-world risk is materially LIMITED: exploitation requires that an attacker already controls the contents of a source container AND that a host administrator subsequently runs lxc-copy on that container, so it is a local, privilege-escalation/container-escape primitive rather than a remotely reachable one. There is no evidence of active exploitation (no KEV) and no public exploit is referenced; treat this as a defense-in-depth hardening fix, not an emergency, pending confirmation of the CVSS vector and affected versions from an Ubuntu/LXC advisory. Note the sharp contrast between potential technical impact (root arbitrary write) and low likelihood signals (local vector, admin action required, no exploitation evidence).

An attacker who controls a container's root filesystem replaces the file that lxc-copy rewrites during a clone (e.g. the hostname/config file) with a symlink pointing to a sensitive host path. When a host administrator later runs lxc-copy to duplicate that container, the root-privileged host-context write follows the symlink and clobbers the targeted host file, yielding arbitrary file write as root and container escape. No public exploit code is referenced; the attack is local and requires the admin-initiated copy action.