CVE-2026-78124

strongSwan 5.0.2 through 6.0.7 contains a memory leak (CWE-401) in the openssl plugin's PKCS#7 certificate enumeration path: certificates parsed during enumeration are not freed after their effective lifetime, so memory is retained on the daemon. The flaw is reachable over the network with no privileges or user interaction, though exploitation requires high attack complexity, and it carries a minor confidentiality impact — an unauthenticated party interacting with certificate handling can enumerate PKCS#7 certificate information while gradually leaking memory in the process. Any deployment of strongSwan 5.0.2–6.0.7 built with the openssl plugin is affected, which includes most standard distribution and router packages. The severity is low (CVSS 3.1: 3.7), there is no known public proof of concept, the issue is not on the CISA KEV list, and no exploitation has been observed. Ubuntu has shipped fixes via security notice USN-8789-1, indicating patched packages are rolling out through downstream distributions.

What to do: Update to a strongSwan release containing the fix (any version later than 6.0.7, or your distribution's patched package, e.g., Ubuntu's USN-8789-1). If you build strongSwan from source and don't need the openssl plugin, build without it or restrict which certificate plugins are loaded. Restrict IKE (UDP 500/4500) exposure at the firewall to known peer addresses, and monitor the charon daemon's memory consumption for unexplained growth on internet-facing VPN gateways.