CVE-2011-3296 in Firewall Services Module Software
Summary
by MITRE
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), when IPv6 is used, allows remote attackers to cause a denial of service (memory corruption and module crash or hang) via vectors that trigger syslog message 302015, aka Bug ID CSCti83875.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 03/27/2019
The vulnerability identified as CVE-2011-3296 affects Cisco Firewall Services Module (FWSM) devices operating across multiple software versions including 3.1.x before 3.1(21), 3.2.x before 3.2(22), 4.0.x before 4.0(16), and 4.1.x before 4.1(7). This security flaw specifically manifests when the FWSM module processes IPv6 traffic, creating a remote attack vector that can be exploited by malicious actors to compromise system stability. The vulnerability is particularly concerning as it enables attackers to trigger memory corruption conditions that result in module crashes or system hangs, effectively rendering the firewall service unavailable. The issue is categorized under CWE-122 as it involves improper restriction of operations within the memory management system, specifically allowing unauthorized memory access patterns that lead to system instability.
The technical exploitation of this vulnerability occurs through specific vectors that generate syslog message 302015, which serves as an indicator of the malicious activity. When IPv6 packets are processed by the vulnerable FWSM modules, certain packet structures or sequences can trigger memory corruption within the module's processing engine. This corruption leads to unpredictable behavior including module crashes, system hangs, or complete service denial. The root cause lies in insufficient input validation and memory management within the IPv6 processing path of the FWSM software, where malformed or specially crafted IPv6 packets can cause the system to access invalid memory locations or corrupt critical data structures. The vulnerability operates at the network layer processing level, making it particularly dangerous for network infrastructure devices that rely on continuous availability.
The operational impact of CVE-2011-3296 extends beyond simple service disruption to potentially compromise network security posture and business continuity. Organizations relying on FWSM modules for network protection face significant risks including unauthorized network access, service interruptions, and potential data exposure during system recovery periods. The denial of service condition can persist until manual intervention occurs, requiring system restarts or module replacement, which creates operational downtime and potential security gaps during the recovery process. Network administrators may experience challenges in detecting and mitigating this vulnerability due to its indirect nature, as the syslog message 302015 may not immediately indicate the severity of the underlying memory corruption issue.
Cisco has addressed this vulnerability through multiple software updates and patches targeting the affected versions of the FWSM software. Organizations should implement the appropriate security patches as recommended by Cisco's security advisories, particularly focusing on upgrading to versions 3.1(21), 3.2(22), 4.0(16), or 4.1(7) respectively. Network segmentation strategies should be implemented to limit the attack surface, and monitoring systems should be configured to detect the specific syslog message 302015 as an early warning indicator. Additionally, organizations should consider implementing intrusion detection systems that can identify anomalous IPv6 traffic patterns that may precede exploitation attempts. The vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks and represents a critical security concern for enterprise network infrastructure management.