CVE-2007-3476 in GD Graphics Library
Summary
by MITRE
Array index error in gd_gif_in.c in the GD Graphics Library (libgd) before 2.0.35 allows user-assisted remote attackers to cause a denial of service (crash and heap corruption) via large color index values in crafted image data, which results in a segmentation fault.
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Analysis
by VulDB Data Team • 07/20/2021
The vulnerability identified as CVE-2007-3476 represents a critical array index error within the GD Graphics Library's GIF decoding component, specifically in the gd_gif_in.c file. This flaw exists in libgd versions prior to 2.0.35 and demonstrates a classic buffer over-read condition that can be exploited through carefully crafted malicious GIF image data. The vulnerability operates by manipulating color index values within GIF image headers to trigger invalid memory access patterns during the decoding process.
The technical implementation of this vulnerability stems from inadequate input validation within the GIF parsing routine where the library fails to properly bounds-check color index values against the allocated array dimensions. When processing GIF files with oversized color indices, the library attempts to access memory locations beyond the allocated buffer boundaries, resulting in segmentation faults and potential heap corruption. This type of error falls under the CWE-129 vulnerability category, which specifically addresses improper validation of array indices, and represents a direct descendant of the more general CWE-125 vulnerability related to out-of-bounds read conditions.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attack vectors. Remote attackers can leverage this flaw to crash applications that utilize libgd for image processing, effectively causing service disruption across web applications, image servers, and any system that handles user-uploaded GIF files. The heap corruption aspect introduces additional risks as it may allow for more advanced exploitation techniques, including potential code execution in vulnerable environments, though the primary impact remains focused on system availability and stability.
Mitigation strategies for CVE-2007-3476 require immediate patching of affected libgd installations to version 2.0.35 or later, which contains the necessary bounds-checking fixes. System administrators should implement comprehensive input validation for all image uploads, particularly for GIF files, to prevent malformed data from reaching the processing layer. Network-level defenses can include content filtering mechanisms that inspect and reject suspicious image files based on size, structure, and color table characteristics. Additionally, organizations should maintain updated vulnerability management processes that include regular security assessments of third-party libraries and dependencies, as this vulnerability demonstrates the importance of keeping graphics processing libraries current with security patches. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for network denial of service, while also potentially enabling T1059.007 for remote code execution if exploited further, emphasizing the need for comprehensive defense-in-depth strategies.