A squashfs-tools security update has been released for both Debian GNU/Linux 10 and 11 to address a security issue with traversal outside of the destination directory.

DSA 4967-1: squashfs-tools security update

- -------------------------------------------------------------------------
Debian Security Advisory DSA-4967-1 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
September 04, 2021   https://www.debian.org/security/faq
- -------------------------------------------------------------------------

Package : squashfs-tools
CVE ID : CVE-2021-40153

Etienne Stalmans discovered that unsquashfs in squashfs-tools, the tools
to create and extract Squashfs filesystems, does not validate filenames
for traversal outside of the destination directory. An attacker can take
advantage of this flaw for writing to arbitrary files to the filesystem
if a malformed Squashfs image is processed.

For the oldstable distribution (buster), this problem has been fixed
in version 1:4.3-12+deb10u1.

For the stable distribution (bullseye), this problem has been fixed in
version 1:4.4-2+deb11u1.

We recommend that you upgrade your squashfs-tools packages.

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

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://www.debian.org/security/