CVE-2012-4091 in NX-OS
Summary
by MITRE
The RIP service engine in Cisco NX-OS allows remote attackers to cause a denial of service (engine restart) via a malformed (1) RIPv4 or (2) RIPv6 message, aka Bug ID CSCtj73415.
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Analysis
by VulDB Data Team • 05/26/2021
The vulnerability identified as CVE-2012-4091 represents a critical denial of service weakness within Cisco NX-OS operating systems that affects the Routing Information Protocol service engine. This flaw exists in the RIP implementation across both IPv4 and IPv6 protocols, making it particularly dangerous as it can be exploited through multiple network layers. The vulnerability specifically targets the RIP service engine which is responsible for maintaining routing tables and exchanging routing information between network devices. The issue manifests when the system receives malformed RIP messages that trigger an engine restart, effectively disrupting network connectivity and routing services.
The technical exploitation of this vulnerability occurs through the careful construction of malformed RIP packets that contain invalid data structures or improperly formatted fields within the RIP protocol headers. These malformed messages, when processed by the affected NX-OS systems, cause the RIP service engine to crash and restart automatically. The root cause lies in insufficient input validation within the RIP message parsing routines, where the system fails to properly sanitize or reject malformed packets before attempting to process them. This type of vulnerability falls under CWE-129, which addresses improper validation of input boundaries, and represents a classic example of a buffer overflow or input validation failure that can be leveraged for denial of service attacks. The vulnerability impacts Cisco NX-OS versions that implement RIP protocol support, making it particularly concerning for enterprise networks that rely on these routing protocols for network connectivity.
The operational impact of CVE-2012-4091 extends beyond simple service disruption as it can lead to significant network instability and potential cascading failures within routing infrastructure. When the RIP service engine restarts, it causes temporary loss of routing information and can trigger network convergence issues that affect multiple network segments. Network administrators may experience unexpected downtime as routing tables rebuild and network devices re-establish their routing relationships. The vulnerability can be exploited remotely without authentication requirements, making it particularly dangerous as attackers can trigger the denial of service from external network locations. This characteristic aligns with ATT&CK technique T1499.004 which covers network denial of service attacks and demonstrates how this vulnerability can be used to disrupt network availability and compromise network reliability. The impact is particularly severe in mission-critical environments where continuous network availability is essential for business operations.
Mitigation strategies for CVE-2012-4091 should focus on both immediate protective measures and long-term architectural improvements. Network administrators should implement access control lists to filter RIP traffic at network boundaries, preventing malformed packets from reaching affected systems. Cisco recommends applying the relevant security patches and software updates that address the input validation issues within the RIP service engine. Additional protective measures include implementing monitoring systems to detect unusual RIP traffic patterns and configuring automatic failover mechanisms to minimize service disruption. The vulnerability highlights the importance of proper input validation and robust error handling within network protocol implementations, aligning with security best practices outlined in NIST SP 800-53 and ISO 27001 frameworks. Organizations should also consider implementing network segmentation to limit the potential impact of such vulnerabilities and establish incident response procedures specifically addressing routing protocol failures. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other network protocols and services.