CVE-2012-6615 in FFmpeg
Summary
by MITRE
The ff_ass_split_override_codes function in libavcodec/ass_split.c in FFmpeg before 1.0.2 allows remote attackers to cause a denial of service (NULL pointer dereference and crash) via a subtitle dialog without text.
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Analysis
by VulDB Data Team • 01/18/2022
The vulnerability identified as CVE-2012-6615 represents a critical denial of service weakness within the FFmpeg multimedia framework that affects versions prior to 1.0.2. This flaw resides in the ff_ass_split_override_codes function located within the libavcodec/ass_split.c file, which is responsible for processing advanced subtitle formats. The vulnerability specifically targets the handling of subtitle dialog entries that lack text content, creating a scenario where malformed input can trigger system instability.
The technical implementation of this vulnerability stems from insufficient input validation within the subtitle parsing logic. When FFmpeg encounters an ASS (Advanced SubStation Alpha) subtitle dialog that contains override codes but no actual text content, the ff_ass_split_override_codes function fails to properly handle the null or empty text field. This condition results in a NULL pointer dereference during the processing of override codes, leading to an immediate crash of the application. The flaw operates at the codec level where subtitle data is parsed and interpreted, making it particularly dangerous as it can be triggered through any media file containing maliciously crafted subtitles.
From an operational perspective, this vulnerability presents significant risk to multimedia applications and systems that rely on FFmpeg for video processing and playback. Attackers can exploit this weakness by crafting specially formatted subtitle streams that contain override codes without text content, allowing them to remotely crash media players, streaming servers, or any application that utilizes FFmpeg for subtitle processing. The impact extends beyond simple service disruption as this vulnerability can be leveraged in automated attacks against media servers, content delivery networks, or streaming platforms where subtitle processing is automatically handled. The vulnerability aligns with CWE-476 which identifies NULL pointer dereference as a fundamental weakness in software design that can lead to system crashes and potential exploitation.
The attack surface for CVE-2012-6615 is particularly broad given FFmpeg's widespread adoption across various media processing applications, including popular media players, streaming servers, and content management systems. This vulnerability can be exploited through multiple vectors including video files with embedded malicious subtitles, network streams, or even web-based media applications that automatically process subtitle data. The exploitation requires minimal privileges and can be executed remotely, making it an attractive target for attackers seeking to disrupt media services or perform denial of service attacks against systems processing multimedia content.
Mitigation strategies for this vulnerability primarily involve upgrading to FFmpeg version 1.0.2 or later, where the NULL pointer dereference issue has been resolved through improved input validation and error handling within the subtitle parsing routines. System administrators should also implement proper input sanitization measures when processing user-uploaded media content, including validation of subtitle streams and implementation of proper error handling for malformed data. The vulnerability demonstrates the importance of robust input validation in multimedia processing libraries and aligns with ATT&CK technique T1499 which covers network denial of service attacks through application-level vulnerabilities. Organizations should also consider implementing network segmentation and monitoring for unusual media processing activities that could indicate exploitation attempts, as this type of vulnerability can be used as part of broader attack campaigns targeting multimedia services and streaming platforms.