CVE-2016-6920 in FFmpeg
Summary
by MITRE
Heap-based buffer overflow in the decode_block function in libavcodec/exr.c in FFmpeg before 3.1.3 allows remote attackers to cause a denial of service (application crash) via vectors involving tile positions.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2016-6920 represents a critical heap-based buffer overflow within the FFmpeg multimedia framework's handling of EXR (OpenEXR) image files. This flaw exists in the decode_block function located in libavcodec/exr.c and affects FFmpeg versions prior to 3.1.3, creating a significant security risk for systems that process or render EXR formatted images. The vulnerability specifically manifests when the application encounters tile positions within EXR files, where improper bounds checking allows maliciously crafted input to overwrite adjacent memory regions on the heap. Such memory corruption directly leads to application instability and can result in complete system crashes or denial of service conditions, making it particularly dangerous in environments where FFmpeg is used for automated media processing or web-based content handling.
The technical exploitation of this vulnerability leverages the inherent characteristics of heap memory management and buffer overflow conditions that fall under the CWE-121 category of stack-based buffer overflow, though this specific instance occurs in heap memory space. When FFmpeg processes an EXR file containing malformed tile position data, the decode_block function fails to properly validate the dimensions and positioning parameters before attempting to allocate or access memory buffers. This allows attackers to craft EXR files with oversized or negative tile coordinates that cause the application to write data beyond the allocated buffer boundaries, resulting in heap corruption that ultimately triggers a segmentation fault or application crash. The vulnerability demonstrates a classic lack of proper input validation and memory bounds checking that is commonly addressed through defensive programming practices and memory safety mechanisms.
The operational impact of CVE-2016-6920 extends beyond simple denial of service scenarios, as it represents a potential vector for more sophisticated attacks within multimedia processing environments. Systems utilizing FFmpeg for content ingestion, transcoding, or streaming services become vulnerable to remote exploitation when processing untrusted EXR files, particularly in web applications or content management systems that automatically process user-uploaded media files. The vulnerability can be exploited through various attack vectors including email attachments, web downloads, or file sharing systems where EXR files may be processed without proper sanitization. Security practitioners must consider this vulnerability in the context of the ATT&CK framework's T1203 technique related to Obfuscated Files or Information, as attackers could potentially embed malicious EXR files within larger payloads to avoid detection while exploiting the buffer overflow for system compromise.
Mitigation strategies for CVE-2016-6920 primarily focus on immediate software updates and deployment of patched FFmpeg versions, with the 3.1.3 release specifically addressing the heap overflow condition through enhanced input validation and memory boundary checks. Organizations should prioritize patch management protocols to ensure all systems processing multimedia content are updated with the latest FFmpeg releases, particularly in environments where user-uploaded content is processed or where FFmpeg is integrated into larger applications or services. Additional defensive measures include implementing strict file format validation, deploying sandboxed processing environments for untrusted media files, and establishing content filtering mechanisms that scan for potentially malicious EXR file structures before processing. Network security controls such as web application firewalls and content inspection systems should also be configured to detect and block suspicious EXR file patterns that may indicate attempts to exploit this vulnerability, while system administrators should monitor for unusual application crashes or memory allocation patterns that could indicate exploitation attempts.