CVE-2012-4098 in NX-OS
Summary
by MITRE
The BGP implementation in Cisco NX-OS does not properly filter AS paths, which allows remote attackers to cause a denial of service (BGP service reset and resync) via a malformed UPDATE message, aka Bug ID CSCtn13055.
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Analysis
by VulDB Data Team • 05/26/2021
The vulnerability identified as CVE-2012-4098 represents a critical flaw in Cisco NX-OS BGP implementation that enables remote attackers to execute denial of service attacks against network infrastructure. This issue specifically targets the Autonomous System (AS) path filtering mechanism within the Border Gateway Protocol implementation, creating a scenario where maliciously crafted UPDATE messages can trigger unintended system behavior. The vulnerability manifests when the system receives malformed AS path information that exceeds expected parameters, leading to service disruption rather than simple packet rejection. The flaw affects Cisco NX-OS software versions running BGP services and represents a fundamental weakness in how the system processes routing information from external peers.
The technical root cause of this vulnerability lies in insufficient input validation within the AS path processing logic of the BGP implementation. When a malformed UPDATE message containing excessive or improperly formatted AS path information is received, the NX-OS BGP daemon fails to properly sanitize or reject the invalid data before processing it further. This lack of proper filtering allows the malformed AS path data to propagate through the system's routing decision processes, ultimately causing the BGP service to reset and initiate a full resynchronization cycle. The system's failure to implement adequate bounds checking and validation mechanisms for AS path attributes creates an exploitable condition where an attacker can craft specific UPDATE messages that trigger the service disruption without requiring authentication or privileged access.
The operational impact of CVE-2012-4098 extends beyond simple service interruption, creating cascading effects throughout network infrastructure that can severely impact connectivity and availability. When the BGP service resets and begins resynchronization, it causes temporary routing instability as the system re-establishes peer connections and reprocesses routing tables. Network operators may experience extended periods of routing convergence issues, potentially affecting multiple network segments depending on the scope of BGP peering relationships. The vulnerability particularly affects service providers and enterprise networks that rely heavily on BGP for external connectivity, as the disruption can propagate across multiple autonomous systems and impact customer traffic. Organizations may face significant operational challenges including increased network management overhead, potential service degradation, and the need for emergency maintenance procedures to restore normal routing operations.
Cisco addressed this vulnerability through software updates that implemented enhanced AS path validation and filtering mechanisms within the NX-OS BGP implementation. The recommended mitigation strategy involves applying the appropriate software patches to affected devices, which typically include updated BGP processing logic that properly validates AS path attributes before accepting or processing UPDATE messages. Network administrators should also implement additional monitoring and alerting mechanisms to detect unusual BGP activity patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-129 Input Validation and CWE-20 Improper Input Validation, both of which emphasize the importance of proper data validation in network protocols. From an ATT&CK framework perspective, this vulnerability maps to T1499 Network Denial of Service and T1566 Phishing, as it represents a network-level service disruption that can be initiated remotely without requiring direct system compromise, making it a significant concern for network security posture management and incident response planning.