Debian DSA-6176-1 strongSwan Critical DoS Integer Underflow CVE-2026-25075

The EAP-TTLS plugin doesn't check the length field in the header of
attribute-value pairs (AVPs) tunneled in EAP-TTLS, which can cause an integer
underflow that may lead to a crash. An unauthenticated attacker could exploit
this for a DoS attack by sending a crafted message.

For the oldstable distribution (bookworm), this problem has been fixed
in version 5.9.8-5+deb12u3.

For the stable distribution (trixie), this problem has been fixed in
version 6.0.1-6+deb13u4.

We recommend that you upgrade your strongswan packages.

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

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/