CVE-2011-3362 in libav
Summary
by MITRE
Integer signedness error in the decode_residual_block function in cavsdec.c in libavcodec in FFmpeg before 0.7.3 and 0.8.x before 0.8.2, and libav through 0.7.1, allows remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via a crafted Chinese AVS video (aka CAVS) file.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 11/20/2021
The vulnerability identified as CVE-2011-3362 represents a critical integer signedness error within the FFmpeg multimedia processing library that affects multiple versions of both FFmpeg and libav. This flaw exists in the decode_residual_block function located in the cavsdec.c file, which is responsible for decoding Chinese AVS video format streams. The issue stems from improper handling of signed and unsigned integer operations during the decoding process, creating a condition where maliciously crafted AVS video files can trigger unexpected behavior in the affected software libraries.
The technical implementation of this vulnerability exploits a fundamental flaw in how the decoder processes residual data blocks within the AVS video format. When processing specially crafted input files, the integer signedness error causes incorrect calculations that can lead to memory corruption patterns. This occurs because the code performs operations where signed integers are used in contexts where unsigned integers would be more appropriate, or vice versa, resulting in unexpected overflow conditions and buffer manipulation. The vulnerability specifically targets the decode_residual_block function which handles the decompression of residual data that represents the difference between predicted and actual pixel values in video compression.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable remote code execution, making it particularly dangerous for applications that process untrusted video content. Attackers can craft malicious AVS video files that, when processed by vulnerable software, cause memory corruption that may be exploitable for arbitrary code execution. The memory corruption manifests as application crashes, heap corruption, or potentially more sophisticated exploitation techniques that could allow attackers to execute malicious code with the privileges of the affected application. This makes the vulnerability particularly concerning for media servers, content delivery networks, and applications that automatically process user-uploaded video files.
Organizations and developers should immediately update to patched versions of FFmpeg and libav, specifically versions 0.7.3 and 0.8.2 respectively, to address this vulnerability. The fix implemented in these versions corrects the integer signedness handling within the decode_residual_block function by ensuring proper type casting and validation of integer operations during AVS video decoding. System administrators should also implement network-level filtering to prevent processing of untrusted video content where possible, and consider deploying intrusion detection systems that can identify patterns associated with exploitation attempts. This vulnerability aligns with CWE-190, which addresses integer overflow and underflow conditions, and represents a typical example of how improper integer handling can lead to memory corruption vulnerabilities that may be exploited for remote code execution. The ATT&CK framework categorizes this as a code injection technique through memory corruption, emphasizing the need for proper input validation and integer type handling in multimedia processing libraries.