CVE-2011-3934 in FFmpeg
Summary
by MITRE
Double free vulnerability in the vp3_update_thread_context function in libavcodec/vp3.c in FFmpeg before 0.10 allows remote attackers to have an unspecified impact via crafted vp3 data.
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Analysis
by VulDB Data Team • 01/11/2022
The CVE-2011-3934 vulnerability represents a critical double free error within the FFmpeg multimedia framework's vp3 video codec implementation. This flaw exists in the vp3_update_thread_context function located in libavcodec/vp3.c, affecting FFmpeg versions prior to 0.10. The vulnerability arises when processing crafted vp3 video data, creating a scenario where memory allocated for thread context management is freed twice during the processing lifecycle. Such double free conditions typically occur when a program attempts to release the same memory block multiple times, leading to unpredictable behavior and potential exploitation by malicious actors.
The technical nature of this vulnerability stems from improper memory management within the video decoding pipeline. When FFmpeg processes vp3 encoded video streams, the vp3_update_thread_context function handles the management of thread contexts required for parallel processing of video frames. The double free occurs during the cleanup phase when the function fails to properly track memory allocation states, allowing an attacker to manipulate the decoding process through specially crafted vp3 data packets. This memory corruption vulnerability can lead to heap-based memory corruption, potentially enabling arbitrary code execution or denial of service conditions.
From an operational perspective, this vulnerability presents significant risks to systems processing video content, particularly those utilizing FFmpeg as their multimedia processing library. Attackers can remotely exploit this weakness by crafting malicious vp3 video data that, when processed by vulnerable FFmpeg implementations, triggers the double free condition. The unspecified impact mentioned in the CVE description suggests that exploitation could lead to various outcomes including system crashes, memory corruption, or potentially more severe consequences depending on the execution environment and memory layout. This vulnerability affects web servers, media processing applications, and any system that relies on FFmpeg for vp3 video decoding, making it a widespread concern across multimedia applications.
The vulnerability aligns with CWE-415, which identifies double free conditions as a critical memory management flaw, and can be mapped to ATT&CK technique T1203, which covers exploitation of memory corruption vulnerabilities. Organizations should prioritize updating their FFmpeg installations to version 0.10 or later, where the double free issue has been resolved through proper memory management implementation. Additionally, implementing input validation and sanitization for video streams, along with network segmentation and monitoring for unusual video processing patterns, can help mitigate the risk. The fix typically involves ensuring that memory allocation tracking is properly maintained and that freed memory blocks are not reused inappropriately during thread context updates, preventing the double free scenario from occurring during vp3 video processing operations.