CVE-2006-2906 in GD Graphics Library
Summary
by MITRE
The LZW decoding in the gdImageCreateFromGifPtr function in the Thomas Boutell graphics draw (GD) library (aka libgd) 2.0.33 allows remote attackers to cause a denial of service (CPU consumption) via malformed GIF data that causes an infinite loop.
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Analysis
by VulDB Data Team • 01/18/2025
The vulnerability identified as CVE-2006-2906 resides within the Thomas Boutell graphics draw library commonly known as libgd version 2.0.33. This library serves as a fundamental graphics manipulation tool used across numerous web applications and systems for handling image formats including gif files. The specific flaw manifests in the gdImageCreateFromGifPtr function which is responsible for parsing and creating image objects from gif data. When processing malformed gif files, this function fails to properly validate the LZW compression data structure that is integral to gif format encoding, creating a condition where the decompression algorithm can enter an infinite loop state.
The technical implementation of this vulnerability stems from inadequate boundary checking and loop termination conditions within the LZW decoding routine. GIF files utilize LZW compression algorithm for data compression, and when the decompression process encounters corrupted or malformed LZW data structures, the decoding loop fails to properly detect the end of data or handle error conditions. This allows an attacker to craft specially designed gif files that contain malformed LZW data sequences which cause the decompression routine to iterate indefinitely, consuming excessive cpu cycles and ultimately leading to denial of service conditions. The flaw represents a classic example of insufficient input validation and error handling in compression algorithms, which aligns with CWE-129 Input Validation and CWE-691 Insufficient Control Flow Management.
From an operational perspective, this vulnerability presents a significant risk to web servers and applications that utilize the gd library for gif image processing. Remote attackers can exploit this weakness by uploading or delivering malicious gif files that trigger the infinite loop condition during image parsing operations. The impact extends beyond simple service disruption as the cpu consumption can be sustained for extended periods, potentially exhausting system resources and affecting other legitimate users or services running on the same system. This type of denial of service attack can be particularly effective in web environments where gif files are frequently processed and displayed, making it a preferred target for attackers seeking to disrupt web services.
The mitigation strategies for this vulnerability primarily involve upgrading to patched versions of the libgd library where the LZW decoding routine has been properly hardened against malformed input. System administrators should prioritize updating their gd library installations to versions that contain proper boundary checking and loop termination mechanisms. Additionally, implementing input validation at multiple layers including web application firewalls and content filtering systems can provide additional defense in depth. The vulnerability also highlights the importance of proper error handling in compression algorithms and aligns with ATT&CK technique T1499.004 for Denial of Service via Resource Exhaustion, making it a critical consideration for security hardening efforts and compliance with security frameworks that emphasize robust input validation and error handling practices.