CVE-2016-8595 in FFmpeg
Summary
by MITRE
The gsm_parse function in libavcodec/gsm_parser.c in FFmpeg before 3.1.5 allows remote attackers to cause a denial of service (assert fault) via a crafted AVI file.
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Analysis
by VulDB Data Team • 07/15/2019
The vulnerability identified as CVE-2016-8595 represents a critical denial of service flaw within the FFmpeg multimedia framework, specifically affecting the gsm_parse function located in libavcodec/gsm_parser.c. This issue manifests when processing crafted AVI files that contain malformed GSM audio data, creating a scenario where an attacker can deliberately trigger an assertion failure that results in application termination. The vulnerability exists in FFmpeg versions prior to 3.1.5, making a substantial portion of installations susceptible to this attack vector. The flaw demonstrates the classic characteristics of a buffer over-read or invalid memory access condition that occurs during the parsing of audio stream metadata, where the parser fails to properly validate input data before attempting to process it.
The technical implementation of this vulnerability stems from insufficient input validation within the GSM audio parser component of FFmpeg's codec handling system. When the gsm_parse function encounters a specially crafted AVI file containing malformed GSM audio frames, it fails to properly validate the structure and content of these frames before proceeding with parsing operations. This validation gap allows the function to attempt operations on invalid data structures, ultimately leading to an assertion failure that terminates the application process. The vulnerability operates at the codec parsing layer, which is fundamental to multimedia processing and represents a critical point of failure in the software's input handling pipeline. This type of flaw aligns with CWE-129, which describes improper validation of array indices, and represents a classic case of insufficient bounds checking in parsing functions that handle multimedia data streams.
The operational impact of CVE-2016-8595 extends beyond simple service disruption, as it can be leveraged by remote attackers to perform denial of service attacks against systems processing multimedia content. Attackers can craft malicious AVI files that, when opened by vulnerable FFmpeg implementations, will cause the application to crash or terminate unexpectedly. This vulnerability affects not only standalone FFmpeg applications but also any software that integrates FFmpeg as a multimedia processing library, including content management systems, video editing applications, and streaming platforms. The remote nature of the attack means that exploitation can occur without requiring local access to the target system, making it particularly dangerous in web environments where users may unknowingly trigger the vulnerability through embedded media content. The vulnerability also maps to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion or application crashes.
Mitigation strategies for CVE-2016-8595 primarily focus on upgrading to FFmpeg version 3.1.5 or later, where the vulnerability has been addressed through improved input validation and error handling within the gsm_parse function. System administrators should also implement content filtering mechanisms that scan multimedia files for known malicious patterns before processing them through FFmpeg-based applications. Additional protective measures include deploying network-based intrusion detection systems that can identify suspicious media file patterns and implementing sandboxing techniques to isolate multimedia processing operations. Organizations should also consider implementing input sanitization layers that validate media file structures before they reach the core FFmpeg parser, providing an additional defense in depth mechanism. The fix implemented in version 3.1.5 specifically addresses the assertion failure by adding proper bounds checking and input validation to ensure that the parser handles malformed GSM audio data gracefully without crashing the application.