CVE-2026-77207 The Libreswan Project CVE debrief

Who should care

Libreswan users and administrators should assess exposure and prioritize patching or mitigation to prevent potential crashes and denial of service. This includes reviewing affected versions and patch levels, and implementing compensating controls such as monitoring for suspicious IKE_AUTH packets. Operators, platform administrators, vulnerability management teams, and security teams should coordinate to verify affected deployments and plan remediation.

Why it matters

CVE-2026-77207 is a null pointer dereference bug in Libreswan's PKCS#7 handling code. Libreswan users should assess exposure and prioritize patching or mitigation to prevent potential crashes and denial of service.

• Potential denial of service due to crashes and restarts.
• Need to verify affected versions and patch levels.
• Possible impact on IKE_AUTH packet processing.

Technical summary

The bug is caused by a disagreement between two NSS APIs, SEC_PKCS7ContainsCertsOrCrls() and SEC_PKCS7GetCertificateList(), when handling a SignedData that carries a CRL but no certificates. This leads to a null pointer dereference when Libreswan iterates the certificate list. The issue can cause a crash and restart when a malicious IKE_AUTH packet is received, potentially leading to a denial of service. The bug is triggered when Libreswan decodes an IKE CERT payload of type CERT_PKCS7_WRAPPED_X509 and encounters a SignedData that carries a CRL but no certificates.

Defensive priority

Libreswan users should assess exposure and prioritize patching or mitigation to prevent potential crashes and denial of service.

Recommended defensive actions

• Assess exposure by checking if Libreswan versions 4.7, 5.3.2, or 5.4 are in use.
• Prioritize patching to versions 5.3.3 or 5.4.1.
• Implement compensating controls, such as monitoring for suspicious IKE_AUTH packets.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.

Evidence notes

The CVE record and source item provide details on the null pointer dereference bug in Libreswan's PKCS#7 handling code. The bug can be triggered by a malicious IKE_AUTH packet, leading to a crash and restart.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.