CVE-2012-1342 in Carrier Routing System
Summary
by MITRE
Cisco Carrier Routing System (CRS) 3.9, 4.0, and 4.1 allows remote attackers to bypass ACL entries via fragmented packets, aka Bug ID CSCtj10975.
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Analysis
by VulDB Data Team • 09/11/2020
The Cisco Carrier Routing System CRS vulnerability identified as CVE-2012-1342 represents a significant security flaw in the network infrastructure software that affects versions 3.9, 4.0, and 4.1. This vulnerability specifically targets the system's handling of Access Control List entries, which are fundamental components for network security and traffic filtering. The flaw allows remote attackers to bypass these critical security controls through a sophisticated manipulation of packet fragmentation techniques, creating a potential pathway for unauthorized network access and data exfiltration.
The technical implementation of this vulnerability stems from the CRS software's inadequate processing of fragmented IP packets within its access control mechanisms. When packets are fragmented during network transmission, the system should maintain consistent security policies across all fragments to ensure proper enforcement of ACL rules. However, the flaw in the CRS implementation causes the system to improperly handle these fragmented packets, allowing malicious actors to craft specific packet sequences that can circumvent security policies. This issue falls under the Common Weakness Enumeration category CWE-119, which deals with weakness in memory management and improper handling of fragmented data within network protocols. The vulnerability specifically impacts the packet processing engine's ability to maintain state information across fragmented packets, leading to inconsistent security enforcement.
The operational impact of this vulnerability extends far beyond simple network access control bypass. Organizations relying on Cisco CRS equipment for their carrier-grade routing infrastructure face serious risks including unauthorized network penetration, potential data breaches, and disruption of critical network services. Attackers can exploit this weakness to gain access to protected network segments, potentially escalating privileges and moving laterally within the network infrastructure. The remote nature of the attack means that threat actors can exploit this vulnerability from outside the network perimeter without requiring physical access or prior authentication. This weakness directly aligns with tactics described in the MITRE ATT&CK framework under the T1071.004 technique for application layer protocol: DNS, where attackers can leverage fragmented packets to bypass network security controls and establish persistent access to target networks.
Mitigation strategies for CVE-2012-1342 should include immediate implementation of Cisco's security advisories and software updates that address the packet fragmentation handling flaw. Network administrators should consider implementing additional network segmentation measures and monitoring for unusual packet fragmentation patterns that could indicate exploitation attempts. The vulnerability highlights the importance of robust packet processing validation in network infrastructure software and underscores the need for comprehensive testing of security controls under various network conditions. Organizations should also implement network traffic analysis tools that can detect anomalous fragmentation patterns and maintain strict version control of network equipment to prevent deployment of vulnerable CRS software versions. Regular security assessments and vulnerability scanning should be conducted to ensure all network infrastructure components are properly patched and configured to prevent exploitation of similar weaknesses in the network security architecture.