CVE-2012-2802 in FFmpeg
Summary
by MITRE
Unspecified vulnerability in the ac3_decode_frame function in libavcodec/ac3dec.c in FFmpeg before 0.11 and Libav 0.8.x before 0.8.4 has unknown impact and attack vectors, related to the "number of output channels" and "out of array writes."
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Analysis
by VulDB Data Team • 12/13/2021
The vulnerability identified as CVE-2012-2802 represents a critical security flaw within the FFmpeg multimedia framework that affects versions prior to 0.11 and Libav versions prior to 0.8.4. This issue resides in the ac3_decode_frame function located in libavcodec/ac3dec.c, which handles the decoding of AC-3 audio streams. The vulnerability stems from improper handling of audio channel configuration parameters during the decoding process, creating a scenario where the software fails to properly validate input data before processing. The flaw specifically relates to the "number of output channels" parameter and manifests through out-of-bounds memory write operations that can occur when the decoder encounters malformed or maliciously crafted AC-3 audio data.
From a technical perspective, this vulnerability constitutes a buffer overflow condition that falls under the CWE-121 category of stack-based buffer overflow, though it may also exhibit characteristics of CWE-787 out-of-bounds write. The root cause lies in the insufficient bounds checking of channel count parameters within the audio decoding pipeline, where the software assumes a certain number of output channels without proper validation against the actual data structure boundaries. When processing audio streams with incorrect channel specifications, the decoder attempts to write data beyond the allocated memory boundaries, potentially overwriting adjacent memory regions. This behavior creates opportunities for arbitrary code execution or system instability, as the memory corruption can be leveraged to manipulate program execution flow or cause denial of service conditions.
The operational impact of CVE-2012-2802 extends across multiple threat vectors and attack scenarios that align with the ATT&CK framework's T1203 Suspicious Linking and T1059 Command and Scripting Interpreter techniques. Attackers can exploit this vulnerability by crafting malicious AC-3 audio files that trigger the flawed channel count handling logic, potentially leading to remote code execution when media players or streaming applications process these files. The vulnerability affects applications that utilize FFmpeg or Libav libraries for audio processing, including media players, streaming servers, content management systems, and multimedia applications. Systems running vulnerable software versions are at risk when processing untrusted audio content, making this particularly dangerous in environments where users may encounter malicious media files through web browsing, email attachments, or file sharing platforms.
Mitigation strategies for this vulnerability require immediate software updates to versions that contain the patched ac3_decode_frame implementation. Organizations should prioritize patching all systems running vulnerable FFmpeg or Libav versions, particularly those handling multimedia content from untrusted sources. Additionally, implementing network-level controls such as media content filtering and sandboxing mechanisms can provide defense-in-depth protection. The vulnerability demonstrates the importance of proper input validation and memory boundary checking in multimedia processing libraries, as outlined in the OWASP Top 10 security principles. Security teams should also consider monitoring for exploitation attempts through network traffic analysis, as malicious audio files may exhibit specific patterns when triggering buffer overflow conditions. Regular vulnerability assessments and security audits of multimedia processing components remain essential for maintaining system integrity, particularly in environments where diverse media content is processed or distributed.