CVE-2004-0244 in 6000
Summary
by MITRE
Cisco 6000, 6500, and 7600 series systems with Multilayer Switch Feature Card 2 (MSFC2) and a FlexWAN or OSM module allow local users to cause a denial of service (hang or reset) by sending a layer 2 frame packet that encapsulates a layer 3 packet, but has inconsistent length values with that packet.
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Analysis
by VulDB Data Team • 12/16/2024
The vulnerability identified as CVE-2004-0244 affects Cisco 6000, 6500, and 7600 series routers that utilize the Multilayer Switch Feature Card 2 (MSFC2) along with FlexWAN or OSM modules. This issue represents a critical design flaw in the packet processing mechanism of these network devices, where the system fails to properly validate layer 2 frame headers against the encapsulated layer 3 packet content. The vulnerability resides within the network processing software that handles frame encapsulation and decapsulation operations, specifically when dealing with inconsistent length fields in the frame header that do not match the actual payload data. This type of vulnerability is classified under CWE-129 Input Validation, which encompasses issues where insufficient validation of input parameters leads to system instability or unexpected behavior. The flaw manifests when local users exploit the inconsistent length values in layer 2 frames that contain layer 3 encapsulated packets, creating a scenario where the network device's packet processing engine becomes overwhelmed or enters an undefined state.
The technical implementation of this vulnerability occurs at the network interface level where the MSFC2 card processes incoming frames. When a malformed layer 2 frame arrives with inconsistent length fields, the device's software fails to properly handle the mismatch between the header length indicator and the actual data payload. This inconsistency causes the packet processing engine to either enter an infinite loop during validation checks or attempt to access memory locations that do not correspond to the actual packet data. The system's failure to properly validate packet headers before processing creates a condition where legitimate network operations become disrupted, leading to the device experiencing a hang or complete reset. The operational impact extends beyond simple service disruption as this vulnerability can be exploited locally, meaning that an attacker with access to the network device or the ability to send crafted packets to the device can trigger the condition without requiring external network access. This local exploit capability significantly increases the threat surface and potential for denial of service attacks.
The operational consequences of this vulnerability are severe for network infrastructure, particularly in enterprise and service provider environments where these Cisco devices serve as critical core routing equipment. When a device experiences a hang or reset due to this vulnerability, it can result in complete network outages or significant service degradation across affected network segments. The device's reset behavior causes all active connections to be dropped and requires manual intervention to restore normal operations, leading to extended downtime and potential loss of network connectivity for connected systems. Network administrators must be aware that this vulnerability can be triggered through legitimate network traffic patterns, making detection and prevention challenging. The vulnerability aligns with ATT&CK technique T1499.004 Network Denial of Service which focuses on disrupting network services through various methods including exploitation of device-specific flaws. Organizations using affected Cisco hardware must implement immediate mitigations including firmware updates, network segmentation to limit local access, and monitoring for suspicious packet patterns that might indicate exploitation attempts.
Cisco addressed this vulnerability through firmware updates that enhanced the packet validation mechanisms within the MSFC2 module, specifically improving the handling of inconsistent length fields in layer 2 frames. The recommended remediation involves upgrading to the latest software releases that contain proper input validation and error handling for frame processing operations. Network administrators should also implement monitoring solutions that can detect unusual packet patterns or potential exploitation attempts, particularly focusing on layer 2 frames with inconsistent length indicators. The vulnerability demonstrates the importance of robust input validation in network infrastructure devices and highlights how seemingly minor inconsistencies in packet headers can lead to catastrophic system failures. Organizations should conduct regular security assessments of their network infrastructure to identify similar vulnerabilities in other network devices that may be susceptible to similar exploitation techniques. This vulnerability serves as a reminder that network devices must implement comprehensive validation mechanisms to prevent malformed packets from causing system instability or complete service disruption, particularly in critical infrastructure environments where availability is paramount.