CVE-2011-4007 in IOS XE
Summary
by MITRE
Cisco IOS 15.0 and 15.1 and IOS XE 3.x do not properly handle the "set mpls experimental imposition" command, which allows remote attackers to cause a denial of service (device crash) via network traffic that triggers (1) fragmentation or (2) reassembly, aka Bug ID CSCtr56576.
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Analysis
by VulDB Data Team • 01/29/2018
The vulnerability described in CVE-2011-4007 represents a critical denial of service flaw affecting Cisco IOS versions 15.0 and 15.1 along with IOS XE 3.x releases. This issue stems from improper handling of the "set mpls experimental imposition" command within the network operating system, creating a scenario where maliciously crafted network traffic can trigger device instability and complete system failure. The vulnerability specifically manifests when the affected Cisco devices process network packets that require either fragmentation or reassembly operations, leading to unpredictable behavior that ultimately results in device crashes and service disruption.
The technical root cause of this vulnerability lies in the insufficient validation and handling of MPLS (Multiprotocol Label Switching) experimental imposition commands within the IOS processing pipeline. When the system encounters network traffic that necessitates fragmentation or reassembly operations, the improper implementation of the mpls experimental imposition command causes memory corruption or stack overflow conditions. This flaw operates at the network protocol processing layer where the IOS kernel handles packet forwarding and label manipulation, making it particularly dangerous as it can be triggered through normal network operations without requiring authentication or elevated privileges. The vulnerability falls under CWE-121, which describes stack-based buffer overflow conditions, and specifically relates to improper handling of network packet processing during critical operations.
The operational impact of this vulnerability extends far beyond simple service interruption, as it creates potential for widespread network disruption in enterprise and service provider environments. Attackers can remotely exploit this weakness by simply sending specially crafted packets that trigger the fragmentation or reassembly paths, causing the affected Cisco devices to crash and restart automatically. This results in immediate loss of network connectivity for all traffic passing through the compromised device, potentially affecting critical business operations, network redundancy systems, and overall network availability. The vulnerability's remote exploitability means that attackers do not need physical access or network proximity to cause disruption, making it particularly concerning for organizations relying on Cisco networking equipment. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 (Network Denial of Service) and T1595.001 (Network Denial of Service), demonstrating how attackers can leverage protocol implementation flaws to compromise network infrastructure availability.
Mitigation strategies for this vulnerability require immediate implementation of Cisco's recommended security patches and updates, as well as network segmentation and traffic filtering approaches to prevent exploitation. Organizations should disable or restrict the use of the affected "set mpls experimental imposition" command until proper firmware updates are deployed. Network administrators should also implement monitoring solutions to detect abnormal traffic patterns that might indicate exploitation attempts, while maintaining robust backup and recovery procedures for network infrastructure. The vulnerability highlights the importance of regular security assessments and prompt patch management for critical network infrastructure components, particularly those handling complex protocol processing functions. Additionally, implementing proper network access controls and intrusion detection systems can help identify and prevent exploitation attempts before they can cause significant damage to network operations.