CVE-2024-2357 in Libreswan
Summary
by MITRE • 03/11/2024
The Libreswan Project was notified of an issue causing libreswan to restart under some IKEv2 retransmit scenarios when a connection is configured to use PreSharedKeys (authby=secret) and the connection cannot find a matching configured secret. When such a connection is automatically added on startup using the auto= keyword, it can cause repeated crashes leading to a Denial of Service.
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Analysis
by VulDB Data Team • 12/02/2024
The vulnerability identified as CVE-2024-2357 affects the Libreswan IPsec implementation, specifically targeting IKEv2 retransmission handling when PreSharedKeys authentication is configured. This issue represents a critical flaw in the cryptographic security infrastructure that underpins secure network communications. The vulnerability manifests when the system attempts to establish an IKEv2 connection using pre-shared keys for authentication, but encounters a scenario where no matching secret exists in the configuration. The Libreswan project, which provides open-source IPsec implementations for Linux systems, has identified this as a condition that triggers unexpected restart behavior during the retransmission process of IKEv2 negotiations.
The technical mechanism behind this vulnerability involves the interaction between IKEv2 protocol handling and the pre-shared key validation process within Libreswan's implementation. When a connection is configured with authby=secret and the system cannot locate a matching secret for the authentication process, the retransmission logic within the IKEv2 state machine triggers an improper error handling condition. This condition causes the libreswan daemon to restart itself rather than gracefully handling the authentication failure. The restart behavior is particularly problematic when the connection is configured with auto= keyword, which automatically adds connections during system startup, creating a cascading effect that can lead to repeated crashes and system instability.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network security infrastructure. When multiple connections are configured with auto= and pre-shared key authentication, the system becomes vulnerable to repeated restart cycles that can render the IPsec service unavailable for legitimate network traffic. This Denial of Service condition affects any system running Libreswan that has such configurations, particularly in environments where IPsec is critical for secure communications between network zones. The vulnerability is particularly concerning in enterprise environments where IPsec tunnels are used for site-to-site connections, remote access, or secure data transmission between critical systems.
The flaw demonstrates characteristics consistent with CWE-248, an unspecified error in the software that results in an abnormal program termination, and aligns with ATT&CK technique T1499.004 for Network Denial of Service attacks. The vulnerability essentially creates a feedback loop where failed authentication attempts trigger system restarts, making it difficult to distinguish between legitimate service issues and malicious exploitation attempts. Organizations using Libreswan for IPsec implementations should prioritize patching this vulnerability as it represents a direct threat to network availability and can potentially be exploited to disrupt critical communications infrastructure. The recommended mitigation involves updating to the patched version of Libreswan, implementing proper secret management practices to ensure matching authentication credentials, and monitoring for unusual restart patterns in IPsec services. Additionally, network administrators should consider implementing connection monitoring and alerting mechanisms to detect potential exploitation attempts and ensure rapid response to any service disruptions.