CVE-2016-9826 in libav
Summary
by MITRE
libavcodec/ituh263dec.c in libav 11.8 allows remote attackers to cause a denial of service (crash) via vectors involving left shift of a negative value.
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Analysis
by VulDB Data Team • 09/03/2020
The vulnerability identified as CVE-2016-9826 resides within the libavcodec library version 11.8, specifically in the ituh263dec.c component responsible for decoding H.263 video streams. This flaw represents a classic integer overflow condition that can be exploited by remote attackers to trigger a denial of service scenario resulting in application crashes. The vulnerability manifests when the decoder processes malformed H.263 video data containing negative values that are subsequently subjected to left shift operations, a common pattern in video decoding for bit manipulation and data extraction.
The technical exploitation of this vulnerability involves manipulating the bitstream parsing logic within the H.263 decoder where negative integers are encountered during the decoding process. When these negative values undergo left shift operations, they can produce undefined behavior or arithmetic overflow conditions that ultimately lead to memory corruption and application termination. This type of vulnerability falls under CWE-191 Integer Underflow (Wrap or Wraparound) and represents a specific instance of improper handling of signed integer operations in multimedia processing components. The flaw demonstrates a fundamental lack of input validation and proper boundary checking within the video decoding pipeline, particularly in how the decoder handles edge cases in the compressed bitstream format.
From an operational perspective, this vulnerability poses significant risks to systems that process untrusted video content, including media servers, streaming platforms, and multimedia applications that utilize libav for video decoding. The remote attack vector means that adversaries can exploit this flaw without requiring local access or authentication, making it particularly dangerous in web-facing applications. The impact extends beyond simple service disruption as the crash can potentially be leveraged in more sophisticated attacks, including those targeting the broader application ecosystem or as part of larger exploitation chains. The vulnerability affects any system that relies on libav for H.263 video decoding, which includes numerous multimedia frameworks and applications across various operating systems and platforms.
Mitigation strategies for CVE-2016-9826 should prioritize immediate patching of affected libav installations to the latest stable versions that contain the necessary fixes for the integer overflow condition. Organizations should implement robust input validation mechanisms that sanitize and verify all incoming video streams before processing, particularly for applications that handle untrusted content from external sources. Network segmentation and access controls can help limit the potential impact of exploitation attempts, while monitoring systems should be configured to detect unusual application behavior or crash patterns that may indicate exploitation attempts. The fix typically involves adding proper bounds checking and ensuring that signed integer operations are validated before execution, aligning with ATT&CK technique T1499.004 for avoiding or evading defenses through input sanitization and proper error handling. Additionally, implementing sandboxing or containerization techniques for multimedia processing can provide additional layers of protection against potential exploitation attempts that leverage this type of integer overflow vulnerability.