CVE-2008-2734 in ASA 5500
Summary
by MITRE
Memory leak in the crypto functionality in Cisco Adaptive Security Appliance (ASA) 5500 devices 7.2 before 7.2(4)2, 8.0 before 8.0(3)14, and 8.1 before 8.1(1)4, when configured as a clientless SSL VPN endpoint, allows remote attackers to cause a denial of service (memory consumption and VPN hang) via a crafted SSL or HTTP packet, aka Bug ID CSCso66472.
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Analysis
by VulDB Data Team • 08/16/2019
The vulnerability identified as CVE-2008-2734 represents a critical memory leak flaw within the cryptographic processing subsystem of Cisco Adaptive Security Appliance (ASA) 5500 series devices. This weakness specifically affects versions 7.2 prior to 7.2(4)2, 8.0 prior to 8.0(3)14, and 8.1 prior to 8.1(1)4 when configured to operate as clientless SSL VPN endpoints. The issue stems from inadequate memory management during SSL and HTTP packet processing, creating a condition where allocated memory resources are not properly released after cryptographic operations. This vulnerability operates at the intersection of network security infrastructure and memory management, presenting a significant risk to enterprise network availability and security posture.
The technical implementation of this flaw occurs within the SSL VPN clientless endpoint functionality where the ASA device processes incoming SSL and HTTP packets. When malformed or crafted packets are received, the cryptographic processing engine fails to properly deallocate memory structures that were allocated during the SSL handshake and subsequent packet processing phases. This memory leak accumulates over time, gradually consuming available system resources until the device reaches critical memory exhaustion levels. The vulnerability manifests as progressive memory consumption that eventually leads to complete system instability and denial of service conditions, effectively rendering the VPN service unavailable to legitimate users while maintaining the device's operational state.
From an operational impact perspective, this vulnerability creates a persistent threat to network availability and business continuity for organizations relying on Cisco ASA devices for remote access services. Attackers can exploit this weakness through simple network-based attacks requiring only the transmission of specially crafted SSL or HTTP packets, making the attack vector both accessible and low-cost to execute. The memory consumption pattern typically progresses slowly enough to avoid immediate detection while steadily degrading system performance until complete service disruption occurs. This characteristic makes the vulnerability particularly dangerous as it can remain undetected for extended periods while silently consuming resources, eventually causing catastrophic service outages that can impact thousands of remote users simultaneously.
The vulnerability aligns with CWE-401, which specifically addresses improper handling of memory allocation and deallocation, and represents a classic example of memory leak exploitation that can be categorized under the ATT&CK technique T1499.200 for network denial of service attacks. Organizations implementing clientless SSL VPN services on affected ASA devices face significant risk of operational disruption, potential regulatory compliance violations, and increased incident response overhead. The vulnerability's exploitation does not require authentication or specialized knowledge, making it particularly dangerous for environments where security monitoring may not immediately detect the gradual resource consumption pattern. This weakness demonstrates the critical importance of proper memory management in security appliances and highlights the need for comprehensive vulnerability management programs that address both known and emerging threats in network infrastructure components.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Cisco security patches and updates, implementing network segmentation to limit exposure, and establishing monitoring protocols to detect abnormal memory consumption patterns. The recommended remediation involves upgrading to the patched versions of Cisco ASA software where the memory leak handling has been corrected. Additional defensive measures include implementing rate limiting on SSL VPN connections, configuring memory monitoring alerts, and establishing incident response procedures specifically designed to address memory exhaustion scenarios. Security teams should also consider implementing network access controls to restrict access to vulnerable devices and maintain detailed logging of SSL VPN connection patterns to identify potential exploitation attempts.