CVE-2017-9990 in FFmpeg
Summary
by MITRE
Stack-based buffer overflow in the color_string_to_rgba function in libavcodec/xpmdec.c in FFmpeg 3.3 before 3.3.1 allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact via a crafted file.
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Analysis
by VulDB Data Team • 12/09/2022
The vulnerability CVE-2017-9990 represents a critical stack-based buffer overflow affecting FFmpeg's XPM decoder component. This flaw exists within the color_string_to_rgba function located in libavcodec/xpmdec.c, specifically impacting FFmpeg versions 3.3 and earlier. The vulnerability arises when processing specially crafted XPM image files that contain malformed color string data, creating a condition where the application writes beyond the bounds of allocated stack memory. The flaw manifests as a stack buffer overflow that can be triggered through remote exploitation, making it particularly dangerous for applications that process untrusted media content. According to CWE-121, this vulnerability falls under stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent stack memory locations.
The technical implementation of this vulnerability exploits the lack of proper input validation in the color_string_to_rgba function, which processes color specifications from XPM files without adequate boundary checks. When an attacker supplies a maliciously crafted XPM file containing oversized color string data, the function fails to validate the input length against the allocated buffer size, leading to memory corruption. This memory corruption can result in application crashes due to segmentation faults or more sinister outcomes including arbitrary code execution depending on memory layout and exploitation conditions. The vulnerability's remote exploitability stems from FFmpeg's widespread use in media processing applications, web servers, and content management systems that handle user-uploaded files without proper sanitization.
The operational impact of CVE-2017-9990 extends beyond simple denial of service scenarios to potentially enable more sophisticated attacks. While the primary effect is application crash leading to service disruption, the buffer overflow condition creates opportunities for attackers to manipulate program execution flow through stack memory corruption. This vulnerability aligns with ATT&CK technique T1203 by enabling adversaries to cause system instability and potentially gain unauthorized access to systems processing vulnerable media content. The vulnerability affects numerous applications that depend on FFmpeg for video and audio processing, including web browsers, media servers, content management systems, and multimedia applications, creating widespread potential impact across multiple threat vectors.
Mitigation strategies for CVE-2017-9990 primarily focus on immediate patching and deployment of FFmpeg version 3.3.1 or later, which contains the necessary fixes for the buffer overflow condition. Organizations should implement comprehensive input validation mechanisms for all media file processing pipelines, particularly focusing on untrusted content from external sources. Network segmentation and application whitelisting can help limit exposure by restricting access to vulnerable FFmpeg-based applications. Additionally, implementing proper memory protection mechanisms such as stack canaries and address space layout randomization can provide additional defense in depth. Regular security auditing of media processing components and maintaining updated media libraries remain essential practices for preventing exploitation of similar vulnerabilities. The fix implemented in FFmpeg 3.3.1 includes proper bounds checking and input validation to ensure that color string data does not exceed allocated buffer boundaries, effectively resolving the stack overflow condition.