CVE-2011-0393 in ASA
Summary
by MITRE
Cisco Adaptive Security Appliances (ASA) 5500 series devices with software 7.0 before 7.0(8.12), 7.1 and 7.2 before 7.2(5.2), 8.0 before 8.0(5.21), 8.1 before 8.1(2.49), 8.2 before 8.2(3.6), and 8.3 before 8.3(2.7) and Cisco PIX Security Appliances 500 series devices, when transparent firewall mode is configured but IPv6 is not configured, allow remote attackers to cause a denial of service (packet buffer exhaustion and device outage) via IPv6 traffic, aka Bug ID CSCtj04707.
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Analysis
by VulDB Data Team • 12/01/2024
The vulnerability identified as CVE-2011-0393 affects Cisco Adaptive Security Appliances (ASA) 5500 series and PIX Security Appliances 500 series devices operating under specific software versions. This issue manifests when devices are configured in transparent firewall mode without IPv6 support, creating a critical flaw that can be exploited by remote attackers to disrupt network operations. The vulnerability stems from improper handling of IPv6 traffic packets in environments where IPv6 is not explicitly configured, leading to a cascade of operational failures that ultimately result in device outages and service disruption.
The technical flaw resides in the packet processing logic of Cisco ASA and PIX devices when operating in transparent mode without IPv6 configuration. When IPv6 packets are received by these devices, the system fails to properly validate or discard them according to the configured security policies. This misconfiguration causes the device to attempt processing IPv6 traffic even though IPv6 is not enabled or supported in the current configuration, leading to exhaustion of packet buffers within the device memory. The flaw represents a classic case of inadequate input validation and protocol handling, aligning with CWE-20: Improper Input Validation and CWE-119: Improper Restriction of Operations within a Limited Access Scope.
The operational impact of this vulnerability is severe and directly translates to denial of service conditions that can compromise network availability and business continuity. Attackers can exploit this weakness by sending specifically crafted IPv6 packets to the affected devices, causing the packet buffer pools to fill rapidly and eventually leading to complete device outage. This results in network segmentation failures, loss of security enforcement capabilities, and complete disruption of services that depend on these security appliances for network protection. The vulnerability affects multiple generations of Cisco ASA and PIX devices, making it particularly dangerous as it spans several software releases and hardware platforms, requiring extensive remediation efforts across enterprise networks.
Mitigation strategies for this vulnerability involve immediate software patching to the latest available versions that address the IPv6 handling logic in transparent firewall mode. Organizations should also consider implementing network segmentation to prevent unauthorized access to vulnerable devices, configuring explicit IPv6 filtering rules, and monitoring for unusual packet patterns that may indicate exploitation attempts. The solution aligns with ATT&CK technique T1499.004: Endpoint Denial of Service, where adversaries target network infrastructure devices to create service disruptions. Additionally, network administrators should implement proper configuration management practices to ensure that devices are not running in transparent mode without appropriate IPv6 support, and should regularly audit their security appliance configurations to prevent similar vulnerabilities from emerging in the future.