CVE-2007-0967 in Firewall Services Module
Summary
by MITRE
Cisco Firewall Services Module (FWSM) 3.x before 3.1(3.1) allows remote attackers to cause a denial of service (device reboot) via malformed SNMP requests.
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Analysis
by VulDB Data Team • 07/14/2019
The vulnerability identified as CVE-2007-0967 affects Cisco Firewall Services Module FWSM version 3.x prior to 3.1(3.1), representing a critical denial of service weakness that can be exploited remotely. This issue specifically targets the SNMP (Simple Network Management Protocol) processing functionality within the FWSM device, where improper handling of malformed SNMP requests leads to complete device reboot. The vulnerability stems from insufficient input validation and error handling mechanisms within the SNMP service implementation, allowing malicious actors to craft specially crafted SNMP packets that trigger unexpected behavior in the device's processing stack.
The technical flaw manifests when the FWSM device receives malformed SNMP requests that contain invalid or unexpected data structures in their SNMP protocol headers or payload content. These malformed packets bypass normal protocol validation checks and cause the device's SNMP service to enter an unstable state, ultimately resulting in an automatic system reboot. The vulnerability is particularly dangerous because it can be exploited remotely without requiring authentication, making it accessible to any attacker with network access to the device. The root cause aligns with CWE-129, which describes improper validation of length of input buffers, and CWE-20, which covers input validation issues that can lead to buffer overflows or other memory corruption conditions.
From an operational impact perspective, this vulnerability presents a significant threat to network availability and business continuity. When exploited successfully, the device reboot causes immediate disruption to network security services, potentially leaving network segments unprotected during the recovery period. The attack can be executed repeatedly, creating a persistent denial of service condition that can be used to maintain ongoing network disruption. Network administrators face the challenge of maintaining security services while the device reboots and reinitializes, potentially creating windows of vulnerability that attackers could exploit for additional compromises. The vulnerability also impacts the overall security posture by demonstrating inadequate input validation in critical network infrastructure components.
The attack vector for this vulnerability is classified under the MITRE ATT&CK framework as Network Service Scanning, specifically targeting the SNMP protocol services. The exploitation process involves sending malformed SNMP requests to the device's management interface, which can be accomplished through various network reconnaissance tools or custom scripts designed to generate malformed packets. The vulnerability is particularly concerning because it affects the management plane of the device, potentially interfering with legitimate network management activities and monitoring functions. Organizations should consider implementing network segmentation and access controls to limit exposure to this vulnerability, while also ensuring that management interfaces are properly secured and monitored for unusual traffic patterns.
Mitigation strategies should include immediate deployment of Cisco's security advisory patches and firmware updates to version 3.1(3.1) or later, which contain proper input validation fixes for the SNMP service. Network administrators should also implement SNMP access control measures, including restricting SNMP access to trusted management stations only and configuring SNMPv3 with strong authentication and encryption. Additional defensive measures include monitoring network traffic for unusual SNMP patterns, implementing intrusion detection systems to detect malformed SNMP requests, and establishing redundant security infrastructure to minimize the impact of potential exploitation attempts. The vulnerability highlights the importance of regular security patching and proper input validation in network security devices, aligning with industry best practices outlined in NIST SP 800-41 and ISO/IEC 27033 standards for network security management.