CVE-2015-3204 in Libreswan
Summary
by MITRE
libreswan 3.9 through 3.12 allows remote attackers to cause a denial of service (daemon restart) via an IKEv1 packet with (1) unassigned bits set in the IPSEC DOI value or (2) the next payload value set to ISAKMP_NEXT_SAK.
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2015-3204 affects the libreswan implementation of the Internet Key Exchange version 1 protocol, specifically within versions 3.9 through 3.12. This issue represents a denial of service weakness that can be exploited by remote attackers to disrupt the IKE daemon service. The vulnerability stems from insufficient input validation mechanisms within the IKE packet processing logic, where the system fails to properly handle malformed packets containing specific bit patterns in the IPSEC DOI value or inappropriate next payload values.
The technical flaw manifests when the IKE daemon receives an IKEv1 packet with unassigned bits set in the IPSEC DOI value or when the next payload value is incorrectly set to ISAKMP_NEXT_SAK. These specific packet structures bypass normal validation checks and cause the daemon to restart or crash. The IPSEC DOI (Domain of Interpretation) field contains specific bit patterns that define the protocol parameters, and when unassigned bits are set inappropriately, they trigger unexpected behavior in the parsing logic. The ISAKMP_NEXT_SAK value represents a specific payload type that should not appear in certain contexts within the IKEv1 message flow, making its presence inappropriately configured a clear indicator of malformed input.
The operational impact of this vulnerability extends beyond simple service disruption as it can be exploited in a persistent manner to continuously restart the IKE daemon, effectively creating a denial of service condition that undermines the security infrastructure. Network security systems relying on libreswan for IPsec connectivity would experience service interruptions, potentially compromising secure communications between network endpoints. This vulnerability is particularly concerning in environments where continuous secure connectivity is critical, such as enterprise networks, VPN services, or any infrastructure requiring stable IPsec tunnel establishment. The daemon restart behavior can also potentially mask other security issues or provide an attacker with opportunities for further exploitation through service disruption.
From a cybersecurity perspective, this vulnerability aligns with CWE-121, which describes buffer overflow conditions, and represents a classic case of inadequate input validation that leads to service disruption. The attack vector follows ATT&CK technique T1499.004, specifically targeting network denial of service through protocol manipulation. Organizations should implement immediate mitigations including upgrading to libreswan versions beyond 3.12 where this vulnerability has been addressed, implementing network segmentation to limit exposure, and deploying monitoring solutions to detect unusual daemon restart patterns. Additionally, network administrators should configure firewalls to filter packets containing malformed IKEv1 structures and establish robust incident response procedures to handle potential exploitation attempts. The vulnerability demonstrates the importance of proper protocol implementation validation and the necessity of thorough testing for edge cases in security-critical network protocols.