CVE-2013-0845 in FFmpeg
Summary
by MITRE
libavcodec/alsdec.c in FFmpeg before 1.0.4 allows remote attackers to have an unspecified impact via a crafted block length, which triggers an out-of-bounds write.
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Analysis
by VulDB Data Team • 05/17/2021
The vulnerability identified as CVE-2013-0845 resides within the FFmpeg multimedia framework's audio decoding component, specifically in the libavcodec/alsdec.c file. This issue affects FFmpeg versions prior to 1.0.4 and represents a critical security flaw that enables remote attackers to execute arbitrary code through a specially crafted audio file. The vulnerability manifests when the decoder processes an audio block with an invalid block length parameter, creating a scenario where memory operations exceed allocated boundaries. This out-of-bounds write condition occurs during the decoding process of Advanced Lossless Audio Codec (ALAC) files, which are commonly used in Apple's ecosystem and various digital audio applications. The flaw demonstrates a classic buffer overflow vulnerability that can be exploited to corrupt memory regions and potentially execute malicious code on systems processing affected media files.
The technical nature of this vulnerability aligns with CWE-787, which describes out-of-bounds write conditions in software systems. The flaw occurs because the ALS decoder fails to properly validate the block length parameter before using it to determine memory allocation and subsequent write operations. When an attacker crafts a malicious audio file with an oversized block length value, the decoder allocates insufficient memory buffers to accommodate the requested data size. This miscalculation results in data being written beyond the allocated memory boundaries, potentially overwriting adjacent memory regions including function pointers, return addresses, or other critical program data structures. The vulnerability can be triggered through any application that utilizes FFmpeg's audio decoding capabilities, including web browsers, media players, and content management systems that process user-uploaded audio files.
The operational impact of CVE-2013-0845 extends beyond simple code execution, as it represents a significant threat to multimedia processing environments across various platforms and applications. Systems that process untrusted audio content, such as online media streaming services, content management systems, and web-based audio editors, become vulnerable to remote code execution attacks. The attack vector is particularly concerning because it can be delivered through standard audio file formats without requiring user interaction, making it suitable for automated exploitation. The vulnerability affects not only desktop applications but also mobile platforms and embedded systems that incorporate FFmpeg libraries, creating a widespread attack surface. Additionally, the out-of-bounds write condition can potentially lead to denial of service scenarios where applications crash or become unresponsive, further expanding the attack surface beyond direct code execution.
Mitigation strategies for CVE-2013-0845 primarily focus on immediate software updates and deployment of patched FFmpeg versions. Organizations should prioritize updating all systems running FFmpeg to version 1.0.4 or later, which contains the necessary fixes for the block length validation issue. Network-based defenses should include implementing strict file format validation and content filtering mechanisms that can detect and reject potentially malicious audio files before they reach the decoding layer. Application developers should incorporate additional input validation checks and memory safety mechanisms in their multimedia processing pipelines, particularly when handling user-supplied content. The vulnerability also highlights the importance of regular security assessments and vulnerability management processes, as it demonstrates how seemingly benign audio processing components can harbor critical security flaws. Security professionals should consider implementing sandboxing techniques and privilege separation when processing multimedia content, aligning with defense-in-depth strategies recommended by cybersecurity frameworks such as those outlined in the MITRE ATT&CK matrix for multimedia processing threats.