CVE-2007-0959 in Pix Firewall
Summary
by MITRE
Cisco PIX 500 and ASA 5500 Series Security Appliances 7.2.2, when configured to inspect certain TCP-based protocols, allows remote attackers to cause a denial of service (device reboot) via malformed TCP packets.
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Analysis
by VulDB Data Team • 07/14/2019
The vulnerability identified as CVE-2007-0959 affects Cisco PIX 500 and ASA 5500 Series Security Appliances running firmware version 7.2.2. This critical flaw resides within the packet inspection mechanisms of these security devices, specifically when processing certain TCP-based protocols. The vulnerability represents a denial of service condition that can be exploited remotely, potentially causing complete device reboot and service interruption. Security appliances of this nature serve as critical network defense mechanisms, making such vulnerabilities particularly concerning from an operational security perspective.
The technical root cause of this vulnerability stems from improper handling of malformed TCP packets within the protocol inspection engine of the affected Cisco appliances. When these devices encounter specially crafted TCP packets that do not conform to expected protocol structures, the inspection process fails to properly validate the packet contents before processing. This validation failure leads to a buffer over-read or memory corruption condition that ultimately triggers an automatic system reboot. The vulnerability specifically impacts the TCP inspection functionality, which is fundamental to the appliance's ability to monitor and control network traffic flow. The flaw demonstrates characteristics consistent with CWE-125, which describes out-of-bounds read conditions, and CWE-248, which covers exposure of an exception to the calling program.
From an operational impact standpoint, this vulnerability presents significant risk to organizations relying on Cisco PIX and ASA appliances for network security. The remote exploit capability means that adversaries can potentially disrupt network services without requiring physical access or local network credentials. The resulting device reboot creates a service interruption that can last several minutes while the appliance restarts and re-establishes network connections. Network administrators may experience service degradation or complete network outages depending on the appliance's role in the network architecture. The vulnerability also introduces potential for extended downtime if the affected appliances are part of critical network infrastructure or if automated failover mechanisms are not properly configured. This type of vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service, and represents a classic example of how protocol inspection flaws can lead to system stability issues.
Organizations should implement immediate mitigation strategies to address this vulnerability, beginning with firmware updates to versions that contain the necessary security patches. Cisco released updates specifically addressing this vulnerability, and administrators should consult official Cisco Security Advisories for recommended firmware versions. Network segmentation and access control measures can help limit the attack surface by restricting which systems can directly communicate with the affected appliances. Implementing intrusion detection systems that can identify malformed TCP traffic patterns may provide early warning of exploitation attempts. Additionally, organizations should consider deploying redundant security appliances to maintain network availability during patching operations. The vulnerability highlights the importance of maintaining current firmware versions and conducting regular security assessments of network infrastructure components. Regular monitoring of network traffic for anomalous TCP packet patterns can help detect potential exploitation attempts before they result in service disruption.