CVE-2011-3947 in FFmpeg
Summary
by MITRE
Buffer overflow in mjpegbdec.c in libavcodec in FFmpeg 0.7.x before 0.7.12 and 0.8.x before 0.8.11, and in Libav 0.5.x before 0.5.9, 0.6.x before 0.6.6, 0.7.x before 0.7.5, and 0.8.x before 0.8.1, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted MJPEG-B file.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/08/2021
The vulnerability identified as CVE-2011-3947 represents a critical buffer overflow flaw within the MJPEG-B decoding component of FFmpeg and Libav multimedia frameworks. This issue affects multiple versions of these widely-used open source libraries that handle multimedia processing across numerous operating systems and applications. The vulnerability resides in the mjpegbdec.c file which processes MJPEG-B format streams, a variant of the Motion JPEG standard used for video compression. The flaw manifests when these libraries encounter specially crafted MJPEG-B files that contain malformed data structures designed to trigger memory corruption during the decoding process. This vulnerability demonstrates a classic buffer overflow condition where insufficient input validation allows attackers to write beyond allocated memory boundaries, potentially leading to system instability or unauthorized code execution.
The technical exploitation of this vulnerability occurs through the manipulation of MJPEG-B file structures that contain oversized or malformed headers, frame dimensions, or compression parameters. When the affected libraries attempt to parse these crafted inputs, they fail to properly validate the size parameters or memory allocation limits, resulting in buffer overflows that can overwrite adjacent memory locations. This memory corruption typically manifests as application crashes or segmentation faults, but in certain circumstances could potentially be leveraged to execute arbitrary code with the privileges of the affected application. The vulnerability is particularly concerning because FFmpeg and Libav are integrated into countless applications including media players, content management systems, web browsers, and multimedia frameworks, making the attack surface extremely broad. The flaw follows the CWE-121 pattern of stack-based buffer overflow, where insufficient bounds checking allows attackers to overwrite stack variables and potentially control program execution flow.
The operational impact of this vulnerability extends far beyond simple denial of service conditions, as it represents a potential gateway for more sophisticated attacks within multimedia processing environments. When exploited, the vulnerability can cause applications using these libraries to crash repeatedly, leading to service disruption and potential data loss. The remote attack vector means that malicious actors can trigger the vulnerability through network-delivered content without requiring local access or user interaction, making it particularly dangerous for web-based applications that process user-uploaded media files. Attackers could potentially construct malicious MJPEG-B files that not only cause crashes but might also be designed to inject shellcode or manipulate program execution flow through stack-based buffer overflow techniques. This vulnerability affects both the FFmpeg and Libav codebases, which are foundational components in multimedia processing across Linux, Windows, and macOS environments, potentially compromising thousands of applications that depend on these libraries for video and audio processing capabilities.
Mitigation strategies for CVE-2011-3947 require immediate patching of affected software versions to address the buffer overflow conditions in the MJPEG-B decoding routines. System administrators should prioritize updating FFmpeg and Libav installations to versions 0.7.12, 0.8.11, 0.5.9, 0.6.6, 0.7.5, and 0.8.1 or later, which contain the necessary fixes for input validation and memory boundary checking. Organizations should implement network-based filtering to restrict or block MJPEG-B file uploads in applications that process user-generated content, particularly in web applications where such files might be submitted through file upload interfaces. Additional defensive measures include deploying application sandboxing techniques to isolate multimedia processing components and implementing input validation controls that check file headers and size parameters before processing. The ATT&CK framework categorizes this vulnerability under the T1203 technique for Obfuscated Files or Information, where attackers might use crafted media files to bypass traditional security controls. Security monitoring should focus on detecting unusual application crashes, segmentation faults, or unexpected behavior in multimedia processing services that might indicate exploitation attempts. Regular vulnerability assessments should verify that all systems using FFmpeg or Libav libraries are running patched versions to prevent exploitation of this and similar buffer overflow vulnerabilities that could enable more advanced attack vectors.