CVE-2007-2464 in PIX
Summary
by MITRE
Race condition in Cisco Adaptive Security Appliance (ASA) and PIX 7.1 before 7.1(2)49 and 7.2 before 7.2(2)19, when using "clientless SSL VPNs," allows remote attackers to cause a denial of service (device reload) via "non-standard SSL sessions."
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Analysis
by VulDB Data Team • 01/25/2025
The vulnerability described in CVE-2007-2464 represents a critical race condition flaw affecting Cisco Adaptive Security Appliances and PIX firewalls running specific software versions. This issue specifically impacts devices configured with clientless SSL VPN functionality, creating a scenario where remote attackers can exploit timing inconsistencies in the SSL session handling mechanism. The vulnerability stems from improper synchronization of concurrent SSL connection processes, allowing malicious actors to manipulate the device's state machine during SSL session establishment. Such race conditions typically occur when multiple threads or processes attempt to access shared resources simultaneously without proper locking mechanisms, leading to unpredictable behavior and potential system instability.
The technical exploitation of this vulnerability involves initiating non-standard SSL sessions that trigger the race condition within the ASA or PIX device's SSL processing subsystem. When the device receives these malformed or out-of-order SSL handshake sequences, the timing discrepancy between concurrent processing threads causes the system to enter an inconsistent state. This condition ultimately results in a device reload or complete system crash, effectively rendering the firewall unavailable to legitimate users. The flaw operates at the protocol level where SSL session management is handled, making it particularly dangerous as it can be exploited without requiring authentication or privileged access to the device itself. The vulnerability demonstrates poor defensive programming practices where proper thread synchronization and state validation mechanisms were not adequately implemented.
The operational impact of CVE-2007-2464 extends beyond simple denial of service, as it represents a fundamental weakness in the device's ability to maintain stable operation under stress conditions. Organizations relying on clientless SSL VPN functionality for remote access face significant risk of service disruption, potentially affecting business continuity and remote workforce productivity. The vulnerability affects a substantial portion of deployed Cisco security appliances, particularly those in the 7.1 and 7.2 software release series, making it a widespread concern for enterprise security teams. Network administrators may experience unexpected device reboots during normal operations, potentially during critical business hours, leading to unplanned downtime and service interruptions. The exploitability of this vulnerability through remote network access means that attackers can target these devices from outside the network perimeter, amplifying the risk to organizations with exposed firewall configurations.
Mitigation strategies for this vulnerability require immediate software updates to the affected Cisco ASA and PIX device versions, specifically applying the patches released by Cisco as part of their security advisory process. Organizations should prioritize upgrading to versions 7.1(2)49 or later for the 7.1 release series, and 7.2(2)19 or later for the 7.2 release series to address the race condition. Network security teams should also implement monitoring solutions to detect unusual SSL session patterns that might indicate exploitation attempts, though such detection capabilities may be limited given the nature of the vulnerability. Additional defensive measures include restricting access to SSL VPN functionality through firewall rules, implementing rate limiting on SSL connections, and conducting thorough security assessments of the affected devices. This vulnerability aligns with CWE-362, which describes race conditions in software systems, and maps to ATT&CK technique T1499.004 for network denial of service attacks, highlighting the importance of proper synchronization mechanisms in security appliance design. The incident underscores the critical need for robust testing of concurrent processing scenarios in network security devices and demonstrates how seemingly minor implementation flaws can result in significant operational disruptions.