CVE-2026-14957: FIPS mode assertion failure via malicious CERT payload

In FIPS mode, Libreswan's adddecodedcert() function calls CERTExtractPublicKey() and asserts that the result is not NULL. However, CERTExtractPublicKey() returns NULL when public key extraction fails, for example if the RSA exponent is set to 0. A remote attacker can send a malformed X.509 certificate in a CERT payload to trigger the assertion, causing the pluto daemon to abort and restart. Continued exploitation causes a denial of service. No remote code execution is possible. Both IKEv1 and IKEv2 are affected. The vulnerability is only exploitable when both the OS and libreswan are running in FIPS mode and at least one CA certificate is loaded. The CERT payload is processed before peer authentication, so no credentials are needed to exploit this. Configurations using only PreSharedKey (PSK) authentication with no CA certificates loaded in the NSS database are not vulnerable.

— NVD

Libreswan contains a reachable assertion in the X.509 certificate processing path when operating in FIPS mode. After calling CERTExtractPublicKey(), the returned public key is asserted to be non-NULL, although the function may legitimately return NULL if public key extraction fails (for example, when processing a certificate with an RSA exponent of zero). An unauthenticated remote attacker can send a specially crafted CERT payload during an IKEv1 or IKEv2 exchange to trigger the assertion and terminate the daemon, resulting in a denial of service. The issue is only reachable when Libreswan is running in FIPS mode and certificate-based authentication is in use with at least one CA certificate loaded in the Libreswan NSS database; deployments using only Pre-Shared Key (PSK) authentication without loaded CA certificates are not affected.

— Red Hat