CVE-2009-0790 in Strongswan
Summary
by MITRE
The pluto IKE daemon in Openswan and Strongswan IPsec 2.6 before 2.6.21 and 2.4 before 2.4.14, and Strongswan 4.2 before 4.2.14 and 2.8 before 2.8.9, allows remote attackers to cause a denial of service (daemon crash and restart) via a crafted (1) R_U_THERE or (2) R_U_THERE_ACK Dead Peer Detection (DPD) IPsec IKE Notification message that triggers a NULL pointer dereference related to inconsistent ISAKMP state and the lack of a phase2 state association in DPD.
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Analysis
by VulDB Data Team • 08/31/2019
The vulnerability described in CVE-2009-0790 represents a critical denial of service weakness affecting the pluto IKE daemon component within several IPsec implementations including Openswan and Strongswan. This flaw specifically targets the Dead Peer Detection (DPD) functionality that is essential for maintaining secure IPsec tunnels by periodically verifying that remote peers are still active and responsive. The vulnerability manifests when the daemon receives specially crafted R_U_THERE or R_U_THERE_ACK notification messages, which are part of the standard DPD protocol designed to detect when IPsec peers have gone offline or become unreachable.
The technical root cause of this vulnerability lies in a NULL pointer dereference condition that occurs within the ISAKMP state management system of the pluto daemon. When processing these malicious DPD messages, the daemon fails to properly validate the presence of a phase2 state association before attempting to access memory locations that may be uninitialized or null. This inconsistency in state handling creates a scenario where the daemon's memory management routines encounter unexpected null references, leading to immediate termination and subsequent restart of the daemon process. The vulnerability is particularly insidious because it can be triggered remotely without requiring authentication, making it an attractive target for attackers seeking to disrupt network connectivity and security services.
From an operational perspective, this vulnerability poses significant risks to organizations relying on IPsec-based secure communications, as it can be exploited to create persistent denial of service conditions that disrupt critical network services. The automatic restart behavior of the daemon following the crash means that attackers can potentially cause repeated disruptions, effectively exhausting system resources and creating ongoing availability issues. The impact extends beyond simple service interruption since IPsec tunnels often provide essential security services for remote access, site-to-site connections, and secure data transmission, making this vulnerability particularly dangerous in enterprise and infrastructure environments where continuous network availability is paramount. This weakness directly aligns with CWE-476 which describes NULL pointer dereference conditions, and represents a classic example of how improper state validation can lead to system instability.
The exploitation of this vulnerability demonstrates a clear pathway for attackers to leverage standard IPsec protocols against security infrastructure, making it a significant concern for network security teams. Organizations should prioritize immediate patching of affected versions, as the vulnerability exists across multiple major releases of both Openswan and Strongswan implementations. The recommended mitigation strategy involves upgrading to patched versions of the software where the NULL pointer dereference has been corrected and proper state validation has been implemented. Additionally, network administrators should consider implementing monitoring solutions that can detect unusual DPD message patterns and potentially malicious traffic that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to service disruption and denial of service attacks, specifically targeting the availability aspect of the CIA triad and potentially enabling further exploitation through service unavailability.