CVE-2012-4618 in IOS
Summary
by MITRE
The SIP ALG feature in the NAT implementation in Cisco IOS 12.2, 12.4, and 15.0 through 15.2 allows remote attackers to cause a denial of service (device reload) via transit IP packets, aka Bug ID CSCtn76183.
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Analysis
by VulDB Data Team • 12/14/2021
The vulnerability identified as CVE-2012-4618 represents a critical flaw in Cisco IOS NAT implementations affecting versions 12.2, 12.4, and 15.0 through 15.2. This issue specifically targets the Session Initiation Protocol Application Layer Gateway (SIP ALG) functionality which is designed to assist with NAT traversal for VoIP communications. The vulnerability manifests when the device processes transit IP packets that contain specific SIP-related attributes, leading to a complete device reload and subsequent denial of service condition. This represents a significant security concern as it allows remote attackers to disrupt network services without requiring authentication or direct access to the device.
The technical root cause of this vulnerability lies within the SIP ALG processing logic within the NAT implementation of Cisco IOS. When the device encounters transit IP packets that match certain SIP packet patterns, the ALG module fails to properly handle the packet processing, causing an uncontrolled memory access violation or stack corruption within the routing engine. This flaw is classified as a buffer overflow or memory corruption issue according to CWE-121, which specifically addresses unsafe array access conditions that can lead to system instability. The vulnerability occurs during the packet inspection phase where the SIP ALG attempts to parse and modify SIP headers within transit packets, but fails to properly validate packet boundaries or handle malformed data structures.
The operational impact of CVE-2012-4618 extends beyond simple service disruption to encompass complete network availability compromise. When exploited successfully, the vulnerability forces the affected Cisco IOS device to reload its operating system, effectively removing it from service for the duration of the restart process. This can result in widespread communication disruption for organizations relying on VoIP services, as well as potential cascading failures if the affected device serves as a critical network gateway or router. Network administrators may experience significant downtime while investigating the issue and implementing mitigations, with potential business impacts ranging from productivity loss to customer service disruptions. The vulnerability is particularly dangerous in enterprise environments where multiple devices may be simultaneously affected, potentially leading to network-wide outages.
Organizations should implement immediate mitigations including disabling the SIP ALG functionality on affected devices through the configuration command no ip nat service sip. This aligns with the defensive strategies recommended in the MITRE ATT&CK framework under the T1499.004 technique for network disruption attacks. Additionally, implementing access control lists to filter SIP-related traffic or deploying network segmentation strategies can help reduce exposure. Network administrators should also consider upgrading to Cisco IOS versions that contain the patched implementation of the SIP ALG functionality, as these releases include proper input validation and memory management controls. Regular monitoring of network device logs for unusual reload patterns or packet processing anomalies should be implemented as part of ongoing security operations to detect potential exploitation attempts. The vulnerability demonstrates the importance of thorough testing for application layer gateways within network infrastructure and highlights the need for robust input validation mechanisms in all network processing components.