CVE-2019-7635 in Simple DirectMedia Layer
Summary
by MITRE
SDL (Simple DirectMedia Layer) through 1.2.15 and 2.x through 2.0.9 has a heap-based buffer over-read in Blit1to4 in video/SDL_blit_1.c.
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Analysis
by VulDB Data Team • 07/09/2023
The vulnerability identified as CVE-2019-7635 represents a critical heap-based buffer over-read flaw within the Simple DirectMedia Layer library version 1.2.15 and 2.x through 2.0.9. This issue occurs specifically within the Blit1to4 function located in the video/SDL_blit_1.c file of the SDL codebase. The vulnerability arises from insufficient bounds checking during pixel format conversion operations, particularly when handling 1-bit to 4-bit color depth transformations. SDL is a widely-used cross-platform development library that provides low-level access to audio, keyboard, mouse, joystick, and graphics hardware through OpenGL and Direct3D. The library is extensively integrated into numerous gaming applications, multimedia software, and embedded systems, making this vulnerability particularly concerning for the broader software ecosystem.
The technical exploitation of this vulnerability occurs when applications utilizing SDL attempt to perform surface blitting operations between different pixel formats, specifically when converting from 1-bit color depth to 4-bit color depth. During these operations, the Blit1to4 function fails to properly validate the boundaries of memory allocations, leading to a situation where the code attempts to read beyond the allocated heap memory region. This over-read condition can result in information disclosure, system instability, or potentially remote code execution depending on the specific implementation context. The flaw is classified under CWE-125 as an out-of-bounds read, which represents one of the most common and dangerous categories of memory safety vulnerabilities in software systems. The vulnerability is particularly dangerous because it can be triggered through normal multimedia operations without requiring special privileges or complex attack vectors.
The operational impact of CVE-2019-7635 extends across numerous software domains that rely on SDL for graphics rendering and multimedia processing. Applications affected include classic games, multimedia players, embedded systems with graphical interfaces, and various software development tools that utilize SDL for their graphical capabilities. Attackers could potentially exploit this vulnerability to extract sensitive information from memory, cause application crashes, or in some scenarios achieve arbitrary code execution. The vulnerability's presence in both major version branches of SDL 1.x and 2.x means that a vast number of existing applications remain at risk, particularly those that have not been updated to patched versions. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation could potentially involve the execution of malicious code within the application's memory space, and T1068 for exploit for privilege escalation, since the over-read could be leveraged to gain additional system access.
Mitigation strategies for CVE-2019-7635 primarily focus on updating to patched versions of SDL where the buffer over-read has been resolved through proper bounds checking and memory validation. Organizations should prioritize updating their SDL dependencies to versions 1.2.16 or 2.0.10 and later, which contain the necessary fixes for this vulnerability. Additionally, developers should implement defensive programming practices such as validating all buffer boundaries and employing memory safety tools during development cycles. The vulnerability demonstrates the importance of rigorous code review processes and automated memory safety testing, particularly for graphics libraries that handle low-level memory operations. Security teams should monitor their software inventories for SDL usage and ensure proper patch management procedures are in place to prevent exploitation of this and similar vulnerabilities. Organizations should also consider implementing runtime protections such as address space layout randomization and stack canaries to reduce the exploitability of such memory corruption vulnerabilities.