Matthias Gerstner discovered that the --join option of Firejail, a sandbox to restrict an application environment, was susceptible to local privilege escalation to root.

For the oldstable distribution (buster), this problem has been fixed in version 0.9.58.2-2+deb10u3.

For the stable distribution (bullseye), this problem has been fixed in version 0.9.64.4-2+deb11u1.

We recommend that you upgrade your firejail packages.

For the detailed security status of firejail please refer to its security tracker page at: \ https://security-tracker.debian.org/tracker/firejail