CVE-2011-3283 in Carrier Routing System
Summary
by MITRE
Cisco Carrier Routing System 3.9.1 allows remote attackers to cause a denial of service (Metro subsystem crash) via a fragmented GRE packet, aka Bug ID CSCts14887.
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Analysis
by VulDB Data Team • 12/01/2021
The vulnerability identified as CVE-2011-3283 affects Cisco Carrier Routing System version 3.9.1 and represents a significant denial of service weakness that can be exploited remotely by attackers to crash the Metro subsystem. This issue manifests when the system processes fragmented Generic Routing Encapsulation packets, which are commonly used for tunneling and network virtualization purposes in carrier-grade networking environments. The vulnerability specifically targets the handling of fragmented GRE packets within the routing system's Metro subsystem, which is responsible for managing local area network connections and traffic aggregation in carrier networks.
The technical flaw stems from inadequate input validation and packet processing mechanisms within the Cisco Carrier Routing System's GRE protocol implementation. When the system receives a malformed or specially crafted fragmented GRE packet, the processing routine fails to properly handle the fragmentation state, leading to memory corruption or unexpected behavior in the Metro subsystem's packet handling modules. This weakness falls under the category of improper input validation as defined by CWE-20, where the system does not adequately verify the integrity and structure of received network packets before processing them. The vulnerability is particularly concerning because it can be triggered through standard network traffic without requiring authentication or special privileges, making it highly exploitable in real-world scenarios.
The operational impact of this vulnerability extends beyond simple service disruption, as it can compromise the reliability and availability of critical carrier network infrastructure. When the Metro subsystem crashes due to this vulnerability, it can result in complete loss of connectivity for affected network segments, potentially impacting thousands of users and services that depend on the carrier's network infrastructure. Network administrators may experience extended downtime while troubleshooting and applying patches, leading to significant business disruption and potential revenue loss. The vulnerability also represents a potential attack vector for adversaries seeking to disrupt telecommunications services, as demonstrated by the Common Attack Pattern Enumeration and Classification (CAPEC) framework's categorization of such denial of service attacks.
Mitigation strategies for CVE-2011-3283 should prioritize immediate patching of affected Cisco Carrier Routing System installations through official firmware updates provided by Cisco. Network administrators should also implement network segmentation and access control measures to limit the exposure of vulnerable systems to untrusted network traffic. Monitoring and logging mechanisms should be enhanced to detect unusual packet patterns that may indicate exploitation attempts, while implementing rate limiting on GRE packet processing can help reduce the impact of potential attacks. Organizations should also consider deploying intrusion detection systems that can identify and alert on suspicious GRE packet fragmentation patterns, aligning with the defensive techniques outlined in the MITRE ATT&CK framework for network denial of service attacks. The vulnerability highlights the importance of robust input validation in network infrastructure devices and underscores the need for comprehensive security testing of protocol implementations in carrier-grade systems.