CVE-2026-100395LXC: lxc-copy host-context hostname update follows symlink

Official description

LXC is a userspace interface for the Linux kernel containment features used to create and manage system containers. In LXC 7.0.0 and earlier, lxc-copy and the public liblxc clone() API can follow attacker-controlled symbolic links while updating /etc/hostname in a copied container root filesystem. The affected surfaces are lxc-copy and liblxc's public lxc_container::clone() API. The privileged cloning process must run as root. The source rootfs must be attacker-controlled or less trusted. A symlink can be placed at etc/hostname or in an intermediate component. The clone operation preserves the symlink before updating the hostname. The vulnerable write truncates and overwrites an existing file outside the destination rootfs. When root clones an untrusted container without LXC_CLONE_KEEPNAME, the copied symlink can resolve outside the destination rootfs and cause the privileged process to overwrite an existing host file with the destination container name. Unprivileged use and managers with independent cloning implementations are not affected. LXC_CLONE_KEEPNAME avoids the hostname update and therefore the affected write.

Affected packages & fixed versions

Affected products (as reported)

References

• https://github.com/lxc/lxc/security/advisories/GHSA-r23j-58gg-pjjc x_refsource_CONFIRM
• https://github.com/lxc/lxc/commit/6424a91a55efc54edc25ca46e9165bd9f35b50b7 x_refsource_MISC
• https://github.com/lxc/lxc/commit/fa12709a79c2b63b3918297d7505108fcc840eb6 x_refsource_MISC