CVE-2011-0395 in Pix Firewall 520
Summary
by MITRE
Cisco Adaptive Security Appliances (ASA) 5500 series devices with software 8.0 before 8.0(5.20), 8.1 before 8.1(2.48), 8.2 before 8.2(3), and 8.3 before 8.3(2.1), when the RIP protocol and the Cisco Phone Proxy functionality are configured, allow remote attackers to cause a denial of service (device reload) via a RIP update, aka Bug ID CSCtg66583.
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Analysis
by VulDB Data Team • 01/26/2025
The vulnerability described in CVE-2011-0395 affects Cisco Adaptive Security Appliances (ASA) 5500 series devices operating with specific software versions that are susceptible to remote denial of service attacks through manipulation of the Routing Information Protocol (RIP) functionality. This weakness specifically impacts devices configured with both RIP protocol support and Cisco Phone Proxy capabilities, creating a dangerous combination that can be exploited by remote attackers to force device reboots. The vulnerability resides in the handling of RIP updates within the ASA software stack, where improper input validation and processing lead to system instability. This issue represents a significant concern for network security infrastructure as it allows attackers to disrupt critical network services without requiring authentication or physical access to the device. The affected versions include multiple release branches of the ASA software, specifically versions 8.0 before 8.0(5.20), 8.1 before 8.1(2.48), 8.2 before 8.2(3), and 8.3 before 8.3(2.1), indicating a widespread problem across several software releases. The vulnerability is classified under CWE-121, which deals with stack-based buffer overflows, and falls within the ATT&CK framework under the T1499.004 technique for Network Denial of Service, demonstrating how attackers can leverage protocol implementations to cause system-wide disruption.
The technical flaw manifests when the ASA device receives a specially crafted RIP update packet that triggers an improper handling of data within the routing protocol processing module. This occurs specifically in the context where both RIP protocol functionality and Cisco Phone Proxy are enabled simultaneously, creating a condition where malformed RIP updates can cause memory corruption or stack overflow conditions. The vulnerability is particularly dangerous because it requires no authentication credentials to exploit, making it accessible to any remote attacker who can reach the device's network interface. The device's failure to properly validate or sanitize incoming RIP update packets allows malicious data to cause unexpected behavior in the system's memory management, ultimately leading to a complete device reload or reboot. The attack vector is straightforward: an attacker sends a malformed RIP update packet to a vulnerable ASA device, and the device processes this packet in a way that causes a system crash or restart. This type of vulnerability is classified as a remote code execution or denial of service condition that can be triggered over the network without requiring any special privileges or access to the device itself.
The operational impact of this vulnerability is severe for organizations relying on Cisco ASA 5500 series devices for network security and access control. When exploited, the vulnerability results in complete device unavailability, forcing network administrators to manually restart the affected appliances and potentially disrupting network connectivity for extended periods. The automatic device reload can cause cascading failures in network infrastructure, particularly when multiple ASA devices are deployed in redundant configurations, as the coordinated restarts can lead to network segmentation or complete service outages. Organizations may experience significant downtime while investigating and resolving the issue, as the vulnerability requires immediate patching or configuration changes to prevent exploitation. The impact extends beyond simple service disruption to include potential security implications, as attackers could use this vulnerability to create denial of service conditions that mask other attacks or to force administrators into emergency response procedures. Network administrators may also face challenges in detecting exploitation attempts, as the device reload appears as a normal system restart, making it difficult to correlate with malicious activity.
Mitigation strategies for CVE-2011-0395 involve immediate software patching to address the underlying vulnerability in the ASA software versions affected by this issue. Cisco released patches for the specific versions mentioned in the vulnerability description, and organizations should immediately upgrade to the patched software versions to eliminate the risk. Alternative configuration-based mitigations include disabling the RIP protocol functionality on affected devices when it is not required for network operations, and disabling the Cisco Phone Proxy feature if it is not actively used. Network segmentation approaches can also be implemented to limit the attack surface by isolating vulnerable ASA devices from potentially hostile network segments. Organizations should also implement monitoring solutions to detect unusual RIP traffic patterns or device restart events that could indicate exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date security patches and proper configuration management for network security appliances, as the combination of protocol support and specific feature configurations can create unexpected security risks. Regular vulnerability assessments and security audits of network infrastructure should include checks for similar configuration combinations that could present analogous vulnerabilities, as this type of issue often occurs when multiple security features are enabled simultaneously without proper consideration of their interaction patterns.