CVE-2008-4551 in strongSwan
Summary
by MITRE
strongSwan 4.2.6 and earlier allows remote attackers to cause a denial of service (daemon crash) via an IKE_SA_INIT message with a large number of NULL values in a Key Exchange payload, which triggers a NULL pointer dereference for the return value of the mpz_export function in the GNU Multiprecision Library (GMP).
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Analysis
by VulDB Data Team • 08/02/2021
The vulnerability identified as CVE-2008-4551 represents a critical denial of service flaw within strongSwan versions 4.2.6 and earlier. This issue manifests when remote attackers send specially crafted IKE_SA_INIT messages containing an excessive number of NULL values within the Key Exchange payload. The flaw resides in the GNU Multiprecision Library (GMP) implementation where the mpz_export function fails to properly handle these malformed inputs, leading to a NULL pointer dereference condition that ultimately crashes the strongSwan daemon process.
The technical root cause of this vulnerability stems from inadequate input validation within the cryptographic processing pipeline of the IPsec implementation. When the strongSwan daemon receives an IKE_SA_INIT message with excessive NULL values in the Key Exchange payload, the system attempts to process these values through the mpz_export function in GMP. The function returns a NULL pointer when encountering malformed data structures, but the strongSwan code does not properly check for this return value before attempting to dereference it. This classic NULL pointer dereference vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations.
The operational impact of this vulnerability extends beyond simple service disruption as it can be exploited by unauthenticated remote attackers to systematically crash strongSwan daemons across network infrastructure. Network administrators responsible for maintaining IPsec VPN services using affected strongSwan versions face significant operational risks including potential service outages, increased maintenance overhead, and potential exposure of network connectivity gaps during daemon restart periods. The vulnerability affects the availability aspect of the CIA triad by compromising the ability of legitimate users to establish secure connections through the affected VPN infrastructure.
Mitigation strategies for CVE-2008-4551 should prioritize immediate patching of affected strongSwan installations to versions 4.2.7 or later where the issue has been resolved through proper NULL pointer validation in the GMP integration. Network administrators should implement monitoring solutions to detect unusual patterns of IKE_SA_INIT message traffic that may indicate attempted exploitation. Additionally, firewall rules can be configured to limit the number of IKE messages per second from individual sources, and intrusion detection systems should be updated to recognize signatures associated with this specific attack pattern. The vulnerability demonstrates the importance of proper error handling in cryptographic libraries and aligns with ATT&CK technique T1499.004 which covers network denial of service attacks targeting network infrastructure services. Organizations should also consider implementing redundant VPN services and failover mechanisms to minimize impact during potential exploitation events.