CVE-2008-2733 in PIX
Summary
by MITRE
Cisco PIX and 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 client VPN endpoint, do not properly process IPSec client authentication, which allows remote attackers to cause a denial of service (device reload) via a crafted authentication attempt, aka Bug ID CSCso69942.
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Analysis
by VulDB Data Team • 08/16/2019
The vulnerability described in CVE-2008-2733 represents a critical denial of service weakness affecting Cisco PIX and Adaptive Security Appliance (ASA) 5500 series devices. This flaw specifically impacts devices configured as client VPN endpoints and manifests during the IPSec client authentication process. The vulnerability was identified through internal Cisco bug tracking system under identifier CSCso69942 and affects multiple software versions including various releases of the 7.2, 8.0, and 8.1 code branches. The issue stems from insufficient validation mechanisms within the authentication handling code that fails to properly process malformed or crafted authentication attempts from remote attackers.
The technical implementation of this vulnerability exploits a buffer over-read condition within the IPSec authentication processing module of the affected Cisco security appliances. When a malicious actor submits a specially crafted authentication packet containing malformed data structures or unexpected parameter values, the device's authentication handler fails to properly validate the input before attempting to process it. This lack of proper input sanitization creates a scenario where the device's memory management routines encounter unexpected data patterns that cause the system to crash and subsequently reload. The vulnerability specifically targets the IPSec client authentication mechanism, which is fundamental to establishing secure remote access connections through the device.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of critical network security infrastructure. Organizations relying on these devices for remote access connectivity face significant risk of unauthorized service interruption, particularly during peak usage periods or when security personnel are least expecting such disruptions. The device reload caused by this vulnerability effectively removes the security appliance from service until manual intervention occurs, potentially creating windows of exposure where network traffic flows without proper security controls. This type of denial of service attack directly violates the availability principles of the CIA triad and can be particularly damaging in environments where continuous network security is paramount.
From a threat modeling perspective, this vulnerability aligns with attack patterns documented in the MITRE ATT&CK framework under the technique of "Denial of Service" within the Execution and Privilege Escalation domains. The vulnerability presents a clear path for remote attackers to exploit without requiring authentication to the device itself, making it particularly dangerous for organizations with exposed VPN endpoints. The weakness maps to CWE-121, which describes heap-based buffer overflow conditions, though the specific implementation in this case involves improper input validation rather than traditional buffer overflows. Organizations should consider implementing network segmentation and access controls to limit exposure of these devices to untrusted networks, as the vulnerability specifically targets remote attack vectors through the VPN client interface.
The recommended mitigations for this vulnerability include immediate deployment of Cisco's security patches and software updates addressing the specific authentication handling flaws. Organizations should upgrade to the patched versions of software releases 7.2(4)2, 8.0(3)14, and 8.1(1)4 or later, as these releases contain the necessary code modifications to properly validate authentication parameters. Network administrators should also consider implementing additional monitoring and alerting mechanisms to detect unusual authentication patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and defensive programming practices in security-critical systems, and organizations should review their security practices to ensure similar weaknesses do not exist in other components of their network infrastructure.