CVE-2006-7121 in Spa921
Summary
by MITRE
The HTTP server in Linksys SPA-921 VoIP Desktop Phone allows remote attackers to cause a denial of service (reboot) via (1) a long URL, or a long (2) username or (3) password during Basic Authentication.
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Analysis
by VulDB Data Team • 08/01/2019
The CVE-2006-7121 vulnerability affects the HTTP server implementation within Linksys SPA-921 VoIP desktop phone, representing a classic buffer overflow condition that enables remote attackers to execute denial of service attacks. This vulnerability stems from inadequate input validation mechanisms within the device's web server component, which fails to properly handle excessively long input parameters during authentication processes. The affected device operates as a VoIP endpoint that provides web-based management interfaces, making it susceptible to exploitation through network-based attacks targeting its HTTP server functionality.
The technical flaw manifests in three distinct attack vectors that exploit buffer overflow conditions within the device's authentication handling mechanisms. Attackers can trigger the vulnerability by submitting excessively long URLs that exceed the allocated buffer space, or by providing overly long username and password strings during Basic Authentication attempts. These input parameters are processed without proper bounds checking, allowing maliciously crafted input to overwrite adjacent memory locations within the device's memory space. The vulnerability specifically targets the HTTP server's handling of authentication credentials and URL parsing functions, where insufficient input validation permits buffer overflows to occur.
The operational impact of this vulnerability extends beyond simple service disruption, as it enables remote attackers to force the device into a reboot cycle, effectively rendering the VoIP phone inoperable for legitimate users. This denial of service condition can be exploited repeatedly, potentially causing persistent service interruptions that affect business communications and network availability. The vulnerability affects devices that rely on Basic Authentication mechanisms, where credentials are transmitted in base64 encoded format, making the attack surface particularly broad as attackers can target any authentication attempt without requiring prior authentication. The device's reboot behavior indicates that the buffer overflow conditions are severe enough to cause system-level crashes rather than merely terminating specific processes.
The vulnerability aligns with CWE-121, which describes buffer overflow conditions where insufficient boundary checking allows attackers to overwrite adjacent memory locations. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1499.004, which involves network denial of service attacks targeting network infrastructure components. The attack requires minimal privileges and can be executed from remote locations, making it particularly dangerous for enterprise environments where VoIP devices are commonly deployed. Organizations should consider this vulnerability as part of broader network security assessments, particularly in environments where VoIP infrastructure lacks proper network segmentation and access controls.
Mitigation strategies should focus on implementing input validation controls at the network perimeter and within device management systems. Network administrators should deploy firewall rules that limit HTTP traffic to authorized management networks and implement rate limiting to prevent exploitation attempts. Device firmware updates from Linksys should be prioritized to address the underlying buffer overflow conditions in the HTTP server implementation. Additionally, organizations should consider disabling unnecessary web management interfaces and implementing network segmentation to limit potential attack vectors. The vulnerability demonstrates the importance of secure coding practices and input validation in embedded network devices, highlighting the need for comprehensive security testing throughout the device development lifecycle to prevent similar issues in future deployments.