Qualys has discovered a local-privilege escalation (LPE) vulnerability affecting Ubuntu Desktop 24.04 and later:

This flaw (CVE-2026-3888) allows an unprivileged local attacker to escalate privileges to full root access through the interaction of two standard system components: snap-confine and systemd-tmpfiles.

More details are available in the security advisory. Canonical has published updated packages as well as instructions for verifying if a system is vulnerable and how to upgrade if so.