CVE-2011-3303 in Firewall Services Module Software
Summary
by MITRE
Cisco Adaptive Security Appliances (ASA) 5500 series devices, and the ASA Services module in Cisco Catalyst 6500 series devices, with software 7.0 before 7.0(8.13), 7.1 and 7.2 before 7.2(5.4), 8.0 before 8.0(5.25), 8.1 before 8.1(2.50), 8.2 before 8.2(5.6), 8.3 before 8.3(2.23), 8.4 before 8.4(2.7), and 8.5 before 8.5(1.1) and Cisco Firewall Services Module (aka FWSM) 3.1 before 3.1(21), 3.2 before 3.2(22), 4.0 before 4.0(16), and 4.1 before 4.1(7) allow remote attackers to cause a denial of service (device reload) via malformed ILS traffic, aka Bug IDs CSCtq57697 and CSCtq57802.
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Analysis
by VulDB Data Team • 11/23/2021
The vulnerability described in CVE-2011-3303 represents a critical denial of service flaw affecting Cisco Adaptive Security Appliances and Firewall Services Modules across multiple software versions. This issue specifically targets the Internet Location Server (ILS) functionality within Cisco's security infrastructure, which is responsible for managing and distributing routing information within network environments. The vulnerability impacts both the ASA 5500 series appliances and the ASA Services module deployed within Cisco Catalyst 6500 series devices, creating widespread exposure across enterprise network security deployments that rely on these platforms for perimeter protection and traffic control.
The technical exploitation of this vulnerability occurs through the injection of malformed ILS traffic that triggers an unhandled exception within the affected Cisco devices. When processing malformed ILS packets, the devices fail to properly validate incoming data structures, leading to memory corruption and subsequent device reload operations. This behavior stems from insufficient input validation mechanisms within the ILS protocol implementation, allowing attackers to craft specific packet sequences that cause the system to crash and restart automatically. The flaw operates at the network protocol level, making it particularly dangerous as it can be exploited remotely without requiring authentication credentials or physical access to the devices.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire network security infrastructures. When affected devices experience reloads due to malformed ILS traffic, network administrators face immediate operational challenges including temporary loss of network connectivity, disruption of security policies, and potential gaps in network monitoring capabilities. The automatic device reloading process creates a cascading effect where multiple devices may simultaneously restart, leading to extended outages and requiring significant administrative intervention to restore normal operations. This vulnerability particularly affects organizations relying on Cisco ASA appliances for critical network security functions, as the device reloads can occur without warning and may be difficult to distinguish from legitimate system maintenance activities.
Organizations affected by this vulnerability should prioritize immediate remediation through software updates to the latest available versions that contain patches addressing the ILS validation issues. Cisco released multiple software releases including 7.0(8.13), 7.1(5.4), 8.0(5.25), 8.1(2.50), 8.2(5.6), 8.3(2.23), 8.4(2.7), and 8.5(1.1) for ASA devices, along with corresponding FWSM updates to address this specific flaw. Network administrators should implement network segmentation strategies to limit exposure to ILS traffic and consider deploying intrusion detection systems that can identify and block malformed ILS packets. Additionally, organizations should conduct thorough vulnerability assessments to identify all affected devices within their network infrastructure and establish incident response procedures to quickly address any exploitation attempts. This vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and maps to ATT&CK technique T1499.004 for network denial of service attacks, highlighting the importance of robust input validation and network monitoring capabilities in preventing successful exploitation attempts.