High [CVE-2026-12413] IKEv2 Denial of Service via malformed fragmentation

An invalidly formatted IKEv2 fragment causes the Libreswan pluto daemon to crash and restart. Continued exploitation would cause a denial of service.

The function reassemble_v2_incoming_fragments() would ignore unknown outer payloads but still store these in a fixed size array msg_digest.digest[PAYLIMIT]. An off-by-one error in the assertion PASSERT(logger, md->digest_roof digest)) causes the daemon to abort.

No remote code execution is possible. Any configuration that allows IKEv2 connections that do not set fragmentation=no are vulnerable.

IKEv1 is not affected. A flaw was found in Libreswan's IKEv2 fragment reassembly mechanism.

When a VPN gateway processes incoming split network packets (fragments) containing unexpected data, an off-by-one boundary validation error triggers an internal program safety check (assertion failure).

While this flaw does not allow data theft or unauthorized system access, a continuous stream of these packets will lead to a persistent Denial of Service (DoS) for legitimate VPN users. Red Hat Product Security rates this vulnerability as having an Important impact, primarily because it can be exploited remotely without authentication.

However, the actual exposure depends entirely on your specific VPN configuration: ``` Affected Configurations: This vulnerability only impacts IKEv2 connections.