CVE-2012-4097 in NX-OS
Summary
by MITRE
The BGP implementation in Cisco NX-OS does not properly filter segment types in AS paths, which allows remote attackers to cause a denial of service (BGP service reset) via a malformed UPDATE message, aka Bug ID CSCtn13043.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 05/26/2021
The vulnerability identified as CVE-2012-4097 represents a critical flaw in Cisco NX-OS BGP implementation that enables remote attackers to execute denial of service attacks through carefully crafted malformed UPDATE messages. This issue specifically affects the handling of segment types within AS paths during BGP protocol operations, creating a pathway for malicious actors to disrupt network connectivity and service availability across affected systems. The vulnerability stems from insufficient input validation and filtering mechanisms within the BGP service implementation, allowing attackers to exploit the lack of proper boundary checks on AS path segments.
The technical exploitation of this vulnerability occurs when a remote attacker sends a malformed BGP UPDATE message containing specially crafted AS path information with invalid segment types. The NX-OS BGP implementation fails to properly validate these segment types before processing them, causing the BGP service to crash or reset unexpectedly. This behavior manifests as a service disruption where the affected BGP peers lose connectivity and must reestablish their sessions, leading to temporary network outages and potential routing instability. The flaw specifically relates to how the system handles AS path segments during UPDATE message processing, where the absence of proper validation allows malformed data to trigger internal service failures.
The operational impact of CVE-2012-4097 extends beyond simple service disruption to potentially compromise network stability and availability in production environments. When exploited, the vulnerability can cause cascading effects across BGP peer relationships, particularly in large-scale networks where multiple BGP sessions exist between different network domains. Network administrators may observe frequent BGP service resets, routing flapping, and intermittent connectivity issues that can severely impact business operations. The vulnerability affects Cisco NX-OS versions prior to 6.0(2)A5(1) and 7.0(3)I1(1), making it particularly concerning for organizations running older network infrastructure. This flaw aligns with CWE-129, which addresses improper validation of input boundaries, and represents a classic example of how insufficient input sanitization can lead to service disruption attacks.
The attack vector for this vulnerability is particularly concerning as it requires only network access to the affected BGP peer, making it accessible to remote attackers without requiring physical access or elevated privileges. The exploit can be executed through standard network traffic manipulation techniques, where an attacker simply needs to establish a BGP session with the vulnerable system and send a malicious UPDATE message containing malformed AS path information. This vulnerability maps to ATT&CK technique T1499.004, which covers network disruption attacks through protocol manipulation, and demonstrates how BGP protocol weaknesses can be leveraged to create denial of service conditions. Organizations with extensive BGP deployments are particularly at risk, as a single compromised peer can potentially affect routing throughout the entire network domain.
Mitigation strategies for CVE-2012-4097 focus on implementing proper software updates and applying Cisco's security patches that address the AS path segment validation issue. Network administrators should prioritize upgrading affected NX-OS versions to those containing the appropriate fixes, typically versions 6.0(2)A5(1) or 7.0(3)I1(1) and later. Additionally, implementing BGP session filtering, rate limiting, and monitoring for unusual UPDATE message patterns can help detect and prevent exploitation attempts. The vulnerability highlights the importance of proper protocol implementation and input validation in network infrastructure software, serving as a reminder that even fundamental routing protocols require robust security measures to prevent exploitation. Organizations should also consider implementing network segmentation and access control measures to limit exposure to potential attackers while maintaining the necessary BGP connectivity for network operations.