CVE-2015-5479 in libav
Summary
by MITRE
The ff_h263_decode_mba function in libavcodec/ituh263dec.c in Libav before 11.5 allows remote attackers to cause a denial of service (divide-by-zero error and application crash) via a file with crafted dimensions.
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Analysis
by VulDB Data Team • 07/25/2022
The vulnerability identified as CVE-2015-5479 resides within the Libav multimedia framework, specifically in the ff_h263_decode_mba function located in libavcodec/ituh263dec.c. This flaw represents a classic divide-by-zero error that occurs when processing H.263 video streams with specially crafted dimensions. The vulnerability affects Libav versions prior to 11.5, making it a significant concern for systems that rely on this open-source multimedia processing library for video decoding operations. The issue stems from inadequate input validation within the video decoding pipeline, where the decoder fails to properly handle malformed dimension parameters that would lead to mathematical operations with zero denominators.
The technical implementation of this vulnerability demonstrates a clear violation of secure coding practices and can be categorized under CWE-369, which specifically addresses divide-by-zero errors in software implementations. When an attacker crafts a video file with maliciously constructed dimensions, the ff_h263_decode_mba function attempts to perform division operations using values that resolve to zero, causing the application to crash abruptly. This behavior manifests as a denial of service condition that completely terminates the application process, rendering the system unable to process any further video content until manual intervention occurs. The vulnerability operates at the codec level, making it particularly dangerous as it can be triggered through normal video file processing without requiring special privileges or complex exploitation techniques.
From an operational perspective, this vulnerability creates substantial risks for organizations that utilize Libav for video processing, streaming services, or multimedia applications. The remote exploitability means that attackers can trigger the denial of service condition through maliciously crafted video files delivered via web applications, email attachments, or file sharing platforms. The impact extends beyond simple service interruption as it can affect critical infrastructure such as content delivery networks, video streaming platforms, and multimedia processing servers that depend on Libav for their operations. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through application-level exploitation, and represents a fundamental weakness in input validation that can be exploited by adversaries seeking to disrupt services.
Mitigation strategies for CVE-2015-5479 primarily focus on immediate software updates and patches to Libav versions 11.5 and later, which contain the necessary fixes to prevent the divide-by-zero condition. System administrators should prioritize patching all affected systems and implementing proper input validation measures at the application level to prevent malformed video files from reaching the vulnerable decoder functions. Additional protective measures include deploying network-based intrusion detection systems that can identify suspicious video file patterns and implementing sandboxing techniques to isolate video processing operations. Organizations should also consider maintaining up-to-date threat intelligence feeds to monitor for exploitation attempts targeting this vulnerability and establish incident response procedures for handling denial of service events. The fix implemented in newer Libav versions demonstrates proper error handling and input validation that prevents the mathematical operations from proceeding when invalid dimension values are detected, thereby preventing the application crash that would otherwise occur.