CVE-2011-4579 in libav
Summary
by MITRE
The svq1_decode_frame function in the SVQ1 decoder (svq1dec.c) in libavcodec in FFmpeg 0.5.x before 0.5.7, 0.6.x before 0.6.4, 0.7.x before 0.7.9, and 0.8.x before 0.8.8; and in Libav 0.5.x before 0.5.6, 0.6.x before 0.6.4, and 0.7.x before 0.7.3 allows remote attackers to cause a denial of service (memory corruption) via a crafted SVQ1 stream, related to "dimensions changed."
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Analysis
by VulDB Data Team • 12/12/2021
The vulnerability identified as CVE-2011-4579 represents a critical memory corruption flaw within the SVQ1 video decoder component of FFmpeg and Libav multimedia frameworks. This issue specifically affects the svq1_decode_frame function in the svq1dec.c file, where improper handling of video stream dimensions leads to unpredictable memory behavior. The vulnerability manifests when processing specially crafted SVQ1 streams that contain modified dimension parameters, creating a scenario where the decoder fails to properly validate input data before attempting to allocate or access memory resources. This flaw exists across multiple versions of both FFmpeg and Libav, spanning from 0.5.x through 0.8.x releases, indicating a widespread exposure that affected numerous applications relying on these libraries for video processing capabilities.
The technical implementation of this vulnerability stems from inadequate bounds checking and input validation within the SVQ1 decoder's frame processing logic. When the decoder encounters a stream with altered dimension parameters, it fails to properly verify that these values remain within acceptable ranges or that they are consistent with the expected video frame structure. This deficiency allows attackers to manipulate the decoder into allocating memory blocks of unexpected sizes or accessing memory locations outside of the intended buffer boundaries. The vulnerability operates at the intersection of buffer overflow conditions and memory corruption patterns, where the improper dimension handling causes the decoder to either overwrite adjacent memory regions or attempt to access invalid memory addresses, ultimately leading to system instability and potential crash conditions. The flaw is classified under CWE-125 as an out-of-bounds read, while also exhibiting characteristics of CWE-787, an out-of-bounds write condition, depending on the specific execution path taken during stream processing.
The operational impact of CVE-2011-4579 extends beyond simple denial of service, as it creates opportunities for more sophisticated attacks within multimedia processing environments. Remote attackers can exploit this vulnerability by crafting malicious SVQ1 streams that trigger the memory corruption during playback or processing operations. The vulnerability affects any system that utilizes FFmpeg or Libav libraries for handling SVQ1 video content, including media servers, video transcoding platforms, content delivery networks, and multimedia applications. In practical attack scenarios, this flaw could be leveraged to cause service disruption in streaming applications, potentially leading to complete system crashes or application hangs that prevent legitimate users from accessing video content. The vulnerability's remote exploitability means that attackers do not require local system access, making it particularly dangerous in networked environments where multimedia content is processed automatically without proper user interaction. From an ATT&CK framework perspective, this vulnerability maps to T1203 (Exploitation for Client Execution) and T1499 (Endpoint Denial of Service) as it enables remote code execution through media processing and service disruption through memory corruption.
Mitigation strategies for CVE-2011-4579 primarily involve immediate software updates to patched versions of FFmpeg and Libav libraries. System administrators should prioritize upgrading to versions 0.5.7, 0.6.4, 0.7.9, and 0.8.8 for FFmpeg, and the corresponding Libav releases that contain the necessary fixes for the SVQ1 decoder. Additionally, implementing input validation measures at the application level can provide defense-in-depth protection by filtering or rejecting suspicious SVQ1 streams before they reach the vulnerable decoder component. Network-level mitigations include content filtering and sandboxing of multimedia processing components to limit the impact of potential exploitation. Organizations should also consider implementing proper error handling and recovery mechanisms that can detect memory corruption conditions and gracefully terminate affected processes rather than allowing system crashes. The vulnerability serves as a reminder of the importance of comprehensive input validation in multimedia processing libraries and highlights the need for regular security auditing of third-party multimedia frameworks used in enterprise environments.