CVE-2012-3950 in IOS
Summary
by MITRE
The Intrusion Prevention System (IPS) feature in Cisco IOS 12.3 through 12.4 and 15.0 through 15.2, in certain configurations of enabled categories and missing signatures, allows remote attackers to cause a denial of service (device reload) via DNS packets, aka Bug ID CSCtw55976.
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Analysis
by VulDB Data Team • 04/14/2021
The vulnerability described in CVE-2012-3950 represents a critical denial of service flaw within Cisco IOS operating systems that affects multiple versions including 12.3 through 12.4 and 15.0 through 15.2. This issue specifically impacts the Intrusion Prevention System feature which is designed to detect and prevent network intrusions. The vulnerability manifests when certain combinations of enabled IPS categories and missing signatures are present in the device configuration, creating a condition where legitimate DNS traffic can trigger system instability. The flaw operates at the network protocol level where specially crafted DNS packets can cause the affected Cisco IOS devices to reload automatically, resulting in complete service disruption.
The technical root cause of this vulnerability lies in improper input validation within the IPS processing engine of Cisco IOS. When the system processes DNS packets that match specific patterns related to the enabled IPS categories, but where corresponding signatures are missing from the configuration, the processing logic fails to handle the malformed packet data correctly. This leads to a buffer over-read condition or memory corruption within the IPS module, ultimately causing the device to crash and automatically reboot. The vulnerability specifically targets the DNS protocol handling within the IPS framework, making it particularly dangerous as DNS is a fundamental protocol for network operations and is frequently targeted by attackers.
The operational impact of this vulnerability extends beyond simple service disruption as it creates a persistent threat vector for attackers seeking to compromise network availability. Organizations with affected Cisco IOS devices face potential business disruption when attackers exploit this vulnerability, as the device reload process can last several minutes and may occur repeatedly if the attack continues. The vulnerability affects the availability aspect of the CIA triad by enabling unauthorized users to consume system resources and force device restarts, effectively creating a denial of service condition that can persist until manual intervention occurs or the device is manually rebooted. Network administrators may find their systems unavailable during critical operational periods, potentially leading to significant downtime and operational costs.
Mitigation strategies for this vulnerability require immediate action from network administrators to address the configuration issues that expose the system to attack. The primary recommendation involves updating the affected Cisco IOS versions to patched releases that contain fixes for the IPS processing logic. Organizations should also review their IPS configuration to ensure that all necessary signatures are properly installed and that enabled categories do not create conflict conditions with missing signature sets. Network segmentation and access control measures should be implemented to limit exposure of vulnerable devices to untrusted networks. Additionally, monitoring systems should be enhanced to detect unusual reload patterns or DNS traffic patterns that may indicate exploitation attempts. This vulnerability aligns with CWE-129 and CWE-772 categories related to input validation and resource management, and represents a technique that could be categorized under ATT&CK tactic TA0040 (Resource Hijacking) and technique T1499.004 (Endpoint Denial of Service) in the MITRE ATT&CK framework.