CVE-2007-3478 in GD Graphics Library
Summary
by MITRE
Race condition in gdImageStringFTEx (gdft_draw_bitmap) in gdft.c in the GD Graphics Library (libgd) before 2.0.35 allows user-assisted remote attackers to cause a denial of service (crash) via unspecified vectors, possibly involving truetype font (TTF) support.
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Analysis
by VulDB Data Team • 07/21/2019
The vulnerability identified as CVE-2007-3478 represents a critical race condition flaw within the GD Graphics Library's text rendering functionality. This issue specifically affects the gdImageStringFTEx function which handles TrueType font processing through the gdft_draw_bitmap subroutine in the gdft.c source file. The vulnerability exists in libgd versions prior to 2.0.35 and enables remote attackers to trigger system crashes through user-assisted means, fundamentally compromising the stability of applications that rely on this graphics library for image processing tasks.
The technical root cause of this vulnerability stems from improper synchronization mechanisms within the font rendering pipeline when processing TrueType font characters. When the gdImageStringFTEx function processes text strings with TTF fonts, it creates a race condition during bitmap generation and memory allocation operations. This race condition manifests when multiple threads or processes attempt to access shared memory resources simultaneously during font rendering operations, leading to memory corruption and subsequent application crashes. The flaw operates at the intersection of concurrent programming issues and graphics processing, making it particularly challenging to detect and exploit consistently.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged by attackers to disrupt critical services that depend on the GD Graphics Library. Applications such as web servers processing image uploads, content management systems, and any software that generates dynamic graphics through text rendering are at risk. The vulnerability's remote exploitation capability means that attackers can trigger crashes without requiring local system access, making it particularly dangerous in web-facing environments where users can submit arbitrary content. This weakness directly relates to CWE-362, which describes race conditions in concurrent programming contexts, and can be classified under ATT&CK technique T1499.004 for network denial of service attacks.
Mitigation strategies for this vulnerability require immediate patching of affected systems to upgrade to libgd version 2.0.35 or later, which contains the necessary synchronization fixes. Organizations should implement comprehensive vulnerability management processes to identify all systems utilizing the GD Graphics Library and ensure timely updates. Additionally, input validation measures should be strengthened to prevent malformed font data from reaching the vulnerable code paths. System administrators should consider implementing network segmentation and monitoring to detect potential exploitation attempts. The fix addresses the underlying race condition by introducing proper mutex locking mechanisms around the critical sections of the font rendering code, ensuring thread-safe memory access during bitmap generation operations. This vulnerability demonstrates the importance of robust concurrent programming practices in graphics libraries and highlights the need for thorough testing of multi-threaded applications that handle external input data.