CVE-2026-14957: 
Rocky Linux vulnerability analysis and mitigation

CVE-2026-14957 is a reachable assertion vulnerability in Libreswan that allows an unauthenticated remote attacker to crash the IKE daemon via a specially crafted X.509 certificate, resulting in a denial of service. The flaw was published on July 15, 2026, with a patch made available on July 17, 2026. It affects Libreswan when running in FIPS mode with certificate-based authentication and at least one CA certificate loaded in the NSS database. It carries a CVSS v3.1 base score of 7.5 (High) (Red Hat Bugzilla, Red Hat CVE).

The vulnerability (CWE-617: Reachable Assertion) exists in Libreswan's X.509 certificate processing path within the FIPS mode code. After calling CERT_ExtractPublicKey(), the code asserts that the returned public key is non-NULL; however, this function can legitimately return NULL when public key extraction fails — for example, when processing a certificate with an RSA exponent of zero. An unauthenticated attacker can send a specially crafted CERT payload during an IKEv1 or IKEv2 exchange to trigger this assertion and terminate the daemon. The vulnerability is only reachable when Libreswan is running in FIPS mode with certificate-based authentication enabled and at least one CA certificate loaded; deployments using only Pre-Shared Key (PSK) authentication without loaded CA certificates are not affected (Red Hat Bugzilla).

Successful exploitation causes the Libreswan IKE daemon to crash, resulting in a complete denial of service for all VPN connections managed by the affected instance. Because no authentication is required and the attack can be launched remotely over the network with low complexity, availability of the VPN service is fully disrupted. There is no confidentiality or integrity impact; the vulnerability is limited to availability (Red Hat Bugzilla, Red Hat CVE).

1. Reconnaissance: Identify targets running Libreswan in FIPS mode with IKEv1 or IKEv2 certificate-based authentication enabled (e.g., by scanning for IKE service on UDP port 500/4500 and probing for FIPS-mode indicators).
2. Craft malicious certificate: Construct a malformed X.509 certificate containing an RSA public key with an exponent of zero or another value that causes CERT_ExtractPublicKey() to return NULL.
3. Embed in CERT payload: Package the malformed certificate into a valid IKEv1 or IKEv2 CERT payload within an IKE exchange message.
4. Send to target: Transmit the crafted IKE message to the target's UDP port 500 or 4500 without any prior authentication.
5. Trigger assertion failure: Libreswan processes the CERT payload, calls CERT_ExtractPublicKey(), receives NULL, hits the assertion, and the daemon process terminates — causing a denial of service for all active and new VPN connections (Red Hat Bugzilla).

• Network: Unexpected or repeated IKE (UDP port 500/4500) connection attempts from unknown sources containing malformed CERT payloads; IKE sessions that terminate abnormally during certificate exchange.
• Logs: Libreswan daemon logs showing assertion failure messages such as assert or Assertion failed related to public key extraction in the X.509 processing path; sudden daemon restart entries in system logs (e.g., systemd reporting libreswan.service crashed or restarted).
• Process: Unexpected termination and restart of the pluto IKE daemon process; core dump files generated by the pluto process in the configured core dump directory.

Red Hat has released patches addressing this vulnerability for Red Hat Enterprise Linux 8 (RHSA-2026:46396), RHEL 9 (RHSA-2026:46397), and RHEL 10 (RHSA-2026:46398). Fedora updates have also been issued. Organizations should apply the available updates immediately, prioritizing systems exposed to untrusted networks. As an interim workaround, consider disabling FIPS mode if operationally feasible, switching to PSK-only authentication, removing CA certificates from the Libreswan NSS database, or applying network-level access controls (firewall rules) to restrict IKE traffic (UDP 500/4500) to trusted peers only (Red Hat Bugzilla, Red Hat CVE).

Coverage of this vulnerability has been limited to standard security advisory channels. Linux security news outlets such as LinuxSecurity.com and Pro-Linux.de reported on the Fedora and RHEL advisories. VulDB catalogued the vulnerability, and Tenable released Nessus detection plugins (IDs 330003, 330061, 330064). No notable researcher commentary or significant social media discussion has been observed beyond routine advisory tracking.