CVE-2008-0531 in Skinny Client Control Protocol
Summary
by MITRE
Heap-based buffer overflow in Cisco Unified IP Phone 7940, 7940G, 7960, and 7960G running SIP firmware might allow remote SIP servers to execute arbitrary code via a crafted challenge/response message.
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Analysis
by VulDB Data Team • 08/05/2019
The vulnerability identified as CVE-2008-0531 represents a critical heap-based buffer overflow affecting Cisco Unified IP Phone models 7940, 7940G, 7960, and 7960G when operating with SIP firmware. This security flaw resides in the telephony device's handling of SIP authentication challenges, specifically within the response message processing mechanism that governs how these IP phones interact with SIP servers. The vulnerability stems from inadequate input validation and bounds checking during the processing of authentication challenge/response exchanges, creating a condition where maliciously crafted SIP messages can trigger memory corruption. The affected devices operate in environments where they must authenticate with SIP servers using digest authentication mechanisms, making them susceptible to exploitation when processing improperly formatted challenge messages. This vulnerability operates at the application layer of the network stack, specifically within the SIP client implementation of the IP phone firmware, and represents a classic buffer overflow scenario where insufficient boundary checks allow data to overwrite adjacent memory locations in the heap allocation.
The technical exploitation of this vulnerability occurs when a remote SIP server sends a crafted challenge message containing an oversized response field that exceeds the allocated buffer size in the phone's memory. When the device processes this malformed message, the excessive data overflows into adjacent heap memory regions, potentially corrupting critical program data structures or executing arbitrary code. The heap-based nature of this overflow means that the memory corruption affects dynamically allocated memory regions rather than stack-based buffers, making exploitation more complex but potentially more reliable in certain environments. Attackers can leverage this vulnerability to execute arbitrary code on the affected devices, potentially gaining full control over the phone's operations and access to the underlying network. The vulnerability specifically targets the authentication processing logic within the SIP stack implementation, where the phone's firmware fails to properly validate the length of incoming response data before copying it into fixed-size buffers. This weakness allows attackers to manipulate memory layout and potentially redirect execution flow through controlled buffer overflows.
The operational impact of this vulnerability extends beyond simple code execution, as compromised IP phones can serve as entry points for broader network infiltration. Once an attacker gains remote code execution capabilities on the phone, they can potentially modify phone configuration settings, intercept voice communications, or use the device as a pivot point for attacking other network components. The vulnerability affects enterprise communication systems where IP phones serve as critical infrastructure components, making the potential impact substantial for organizations relying on Cisco Unified Communications solutions. The remote nature of the attack means that adversaries do not require physical access to the devices, enabling exploitation from anywhere on the network. This vulnerability particularly impacts organizations using SIP-based VoIP infrastructure, as it directly targets the authentication mechanisms that protect these communications systems. The affected devices typically operate in mission-critical environments where unauthorized access could compromise business continuity and security operations. The vulnerability also poses risks to network integrity since compromised phones can be used to launch further attacks or serve as persistent backdoors within the network infrastructure.
Mitigation strategies for CVE-2008-0531 should prioritize immediate firmware updates from Cisco, as the vendor has released patches addressing this specific heap overflow vulnerability. Organizations should implement network segmentation to isolate VoIP infrastructure from general network traffic, reducing the attack surface for potential exploitation. Network-based intrusion detection systems should be configured to monitor for anomalous SIP traffic patterns that might indicate exploitation attempts, particularly focusing on unusual challenge/response message formats. Device configuration hardening measures including disabling unnecessary SIP features, implementing strict authentication mechanisms, and monitoring phone communication logs can help detect and prevent exploitation attempts. The vulnerability aligns with CWE-121, heap-based buffer overflow, and maps to ATT&CK techniques involving remote code execution through network services. Organizations should also consider implementing network access controls to restrict communication between IP phones and untrusted SIP servers, ensuring that only authorized authentication servers can interact with the devices. Regular vulnerability assessments and security audits of VoIP infrastructure are essential to identify and remediate similar vulnerabilities in related network components, as this represents a class of security flaws that may exist in other telephony equipment or SIP implementations.