CVE-2013-4564 in Libreswan
Summary
by MITRE
Libreswan 3.6 allows remote attackers to cause a denial of service (crash) via a small length value and (1) no version or (2) an invalid major number in an IKE packet.
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Analysis
by VulDB Data Team • 01/18/2022
The vulnerability identified as CVE-2013-4564 affects Libreswan version 3.6, a widely used implementation of the Internet Key Exchange protocol for establishing secure communications. This flaw represents a classic denial of service condition that can be exploited by remote attackers to crash the affected system. The vulnerability manifests when the IKE daemon processes malformed packets containing specifically crafted parameters that fall outside expected protocol boundaries. The attack vector requires the remote adversary to send an IKE packet with either no version field or an invalid major version number, combined with a small length value that triggers an improper handling mechanism within the software's packet parsing logic.
The technical root cause of this vulnerability lies in insufficient input validation and error handling within the IKE packet processing components of Libreswan. When the system encounters an IKE packet with an invalid major version number or missing version information, the parsing routine fails to properly validate the packet structure before attempting to process it. This leads to a buffer overflow condition or an invalid memory access pattern that causes the daemon to terminate unexpectedly. The combination of a small length value with malformed version information creates a scenario where the software's memory management routines encounter unexpected data structures that they cannot safely handle, resulting in a crash of the IKE daemon process.
From an operational perspective, this vulnerability presents a significant risk to organizations that rely on Libreswan for secure network communications, particularly those using IPsec VPN services. The denial of service impact means that legitimate users would lose access to secure connections, potentially disrupting business operations and communication channels. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter without requiring any authentication credentials, making it particularly dangerous. The vulnerability affects the core functionality of the IPsec implementation, which could lead to cascading failures in network security infrastructure that depends on stable IKE daemon operations for key exchange and security association establishment.
The vulnerability maps to CWE-125 in the Common Weakness Enumeration catalog, which classifies it as an out-of-bounds read condition that occurs when software reads data past the end of a valid buffer or memory region. This weakness specifically relates to improper input validation where the system fails to check the integrity and validity of incoming data before processing. From the MITRE ATT&CK framework perspective, this vulnerability could be categorized under the T1499.004 technique for Network Denial of Service, where adversaries target network services to disrupt availability. The attack requires minimal privileges and can be executed automatically, making it particularly attractive to threat actors seeking to disrupt network services. Organizations should implement immediate mitigations including patching to the latest Libreswan version, implementing network segmentation to limit exposure, and monitoring for unusual IKE packet patterns that might indicate exploitation attempts.
The impact of this vulnerability extends beyond simple service disruption as it affects the fundamental security infrastructure of networks relying on IPsec implementations. When the IKE daemon crashes, it not only prevents new security associations from being established but can also affect existing connections that may be in the process of renegotiating or authenticating. The lack of proper error handling means that the system does not gracefully recover from malformed input, instead terminating the service entirely. This creates a window of vulnerability where network security is weakened, potentially exposing systems to further attacks that could exploit the temporary service outage. The vulnerability demonstrates the critical importance of robust input validation in security-critical software components, particularly those handling network protocols where malformed packets are common due to both legitimate variations and malicious attempts to exploit software weaknesses.
Organizations should prioritize patching this vulnerability as soon as possible, as the exploitation can occur without authentication and can be automated. The fix typically involves implementing proper bounds checking and validation routines for IKE packet version fields, ensuring that all incoming packets are verified against expected protocol parameters before any processing occurs. Network administrators should also consider implementing IDS/IPS signatures that can detect and block malformed IKE packets with invalid version information, providing an additional layer of protection while patches are deployed. The vulnerability serves as a reminder of the importance of thorough testing of protocol implementations against edge cases and malformed inputs, particularly in security software where robustness is paramount to maintaining network availability and security.