CVE-2026-78133

strongSwan's libcharon, the component implementing IKEv2/IPsec key negotiation in the charon daemon, contains a use-after-free (CWE-416) in its handling of IKEv2 rekeying collisions, affecting versions 6.0.0 through 6.0.7. The flaw is triggered when two peers simultaneously initiate rekeying of the same security association and the daemon frees an object that the colliding rekey transaction still references; because the CVSS vector scores network attack complexity as high with low privileges required, an attacker needs to be a valid (authenticated) IKEv2 peer and hit a timing-dependent race condition. Successful exploitation can crash the VPN daemon, and the high confidentiality/integrity/availability impacts in the score indicate memory corruption that could potentially extend to code execution in the context of the daemon. Anyone running strongSwan 6.0.0 through 6.0.7 as an IKEv2 responder or initiator — including VPN gateways, site-to-site tunnel endpoints, and appliances or distributions that bundle the 6.0.x series — is affected. No public proof-of-concept, in-the-wild exploitation, or CISA KEV listing is known at the time of this analysis.

What to do: Upgrade strongSwan to a release newer than 6.0.7 once the fix is published — check the upstream release notes or security advisories for the patched 6.0.x version, as the affected range ends at 6.0.7. Until then, restrict IKEv2 access (UDP 500/4500) to trusted, authenticated peers via firewall rules or peer allowlists, and monitor VPN gateways for unexpected charon daemon crashes or restarts. Because exploitation requires valid IKEv2 credentials and a hard-to-hit race condition (AC:H), exposure to unauthenticated attackers is limited, but authenticated VPN peers should be treated as potential sources of malicious rekey traffic.