CVE-2010-2821 in Firewall Services Module Software
Summary
by MITRE
Unspecified vulnerability on the Cisco Firewall Services Module (FWSM) with software 3.2 before 3.2(17.2), 4.0 before 4.0(11.1), and 4.1 before 4.1(1.2) for Catalyst 6500 series switches and 7600 series routers, when multi-mode is enabled, allows remote attackers to cause a denial of service (device reload) via crafted (1) Telnet, (2) SSH, or (3) ASDM traffic over TCP, aka Bug ID CSCtg68694.
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Analysis
by VulDB Data Team • 09/22/2021
The vulnerability identified as CVE-2010-2821 represents a critical denial of service weakness affecting Cisco Firewall Services Module (FWSM) implementations across multiple software versions. This flaw specifically manifests within the FWSM running on Catalyst 6500 series switches and 7600 series routers when multi-mode configuration is active. The vulnerability stems from insufficient input validation mechanisms within the FWSM's handling of network traffic, particularly when processing Telnet, SSH, or ASDM communications over TCP protocols. The affected software versions include 3.2 prior to 3.2(17.2), 4.0 prior to 4.0(11.1), and 4.1 prior to 4.1(1.2), indicating this weakness persisted across several major releases of the FWSM software stack.
The technical exploitation of this vulnerability occurs through carefully crafted network packets that leverage the FWSM's processing of authentication and management traffic. When remote attackers send malformed or specially constructed Telnet, SSH, or ASDM traffic to the affected device, the FWSM's internal state management fails to properly handle these inputs, resulting in an abrupt device reload. This behavior constitutes a classic denial of service condition where legitimate network services become unavailable due to the device's forced restart. The vulnerability's impact is particularly severe because it affects management protocols that administrators rely upon for device configuration and monitoring, potentially allowing attackers to disrupt critical network security infrastructure.
From an operational perspective, this vulnerability presents significant risks to network security operations as it can be exploited remotely without requiring authentication credentials. The fact that attackers can trigger device reloads through Telnet, SSH, or ASDM connections means that even unauthorized access attempts could result in service disruption. The multi-mode enabled configuration further compounds the risk by expanding the attack surface to include multiple protocol handling pathways. Network administrators must recognize that this vulnerability can be exploited by malicious actors to create persistent service interruptions, potentially masking more sophisticated attacks or simply causing operational disruption during critical network maintenance windows.
Security professionals should note that this vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and represents a classic example of a buffer overflow or input validation failure that can lead to denial of service conditions. The ATT&CK framework categorizes this weakness under the T1499.004 sub-technique for Network Denial of Service, highlighting the operational impact on network availability. Organizations should implement immediate mitigation strategies including applying the relevant Cisco security patches, disabling unnecessary management protocols, and implementing network segmentation to limit exposure. The vulnerability also underscores the importance of regular security assessments and patch management programs, as it demonstrates how configuration-specific weaknesses can persist across multiple software releases and affect critical infrastructure components.