CVE-2009-4635 in FFmpeg
Summary
by MITRE
FFmpeg 0.5 allows remote attackers to cause a denial of service and possibly execute arbitrary code via a crafted MOV container with improperly ordered tags that cause (1) mov.c and (2) utils.c to use inconsistent codec types and identifiers, leading to processing of a video-structure pointer by the mp3 decoder, and a stack-based buffer overflow.
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Analysis
by VulDB Data Team • 04/30/2026
The vulnerability identified as CVE-2009-4635 represents a critical security flaw in FFmpeg version 0.5 that demonstrates the dangerous consequences of improper input validation and inconsistent data handling within multimedia processing frameworks. This vulnerability specifically affects the MOV container format processing within FFmpeg, where maliciously crafted media files can trigger a cascade of processing errors that ultimately lead to system compromise. The flaw resides in how the software handles container metadata and codec information, creating a scenario where legitimate processing logic becomes corrupted by malformed input data.
The technical implementation of this vulnerability exploits inconsistencies between mov.c and utils.c components within the FFmpeg codebase, where improperly ordered tags within the MOV container cause the system to use mismatched codec types and identifiers. This fundamental mismatch occurs when the software encounters a crafted MOV file containing tags that do not follow the expected sequence or structure, leading to a scenario where video-structure pointers are incorrectly processed by the mp3 decoder component. The underlying issue stems from insufficient validation of container tag ordering and type consistency, allowing attackers to manipulate the internal state of the media processing engine.
This vulnerability creates a particularly dangerous condition because it can lead to both denial of service and arbitrary code execution, making it a severe threat to systems that process multimedia content. The stack-based buffer overflow that results from this flaw occurs when the mp3 decoder receives a malformed video-structure pointer, causing memory corruption that can be exploited by attackers to execute malicious code with the privileges of the affected process. The vulnerability demonstrates how seemingly isolated processing errors can compound into critical security issues when different components within a multimedia framework fail to maintain consistent data state.
The operational impact of CVE-2009-4635 extends beyond simple service disruption to potentially enable full system compromise, particularly in environments where FFmpeg is used for processing untrusted media content. Systems that rely on FFmpeg for video transcoding, streaming, or content ingestion are at risk when processing maliciously crafted MOV files, as the vulnerability can be exploited through various attack vectors including web applications, email attachments, or file sharing systems. The exploitability of this vulnerability is enhanced by the fact that MOV containers are widely supported and used across multiple platforms, making the attack surface particularly broad.
Security practitioners should consider this vulnerability in the context of CWE-121, which addresses stack-based buffer overflow conditions, and CWE-20, which covers improper input validation. The ATT&CK framework categorizes this vulnerability under T1203, which involves exploiting software vulnerabilities for privilege escalation, and T1059, which covers command and scripting interpreter techniques. Mitigation strategies should include immediate patching of FFmpeg to versions that address the tag ordering validation issues, implementing strict input validation for multimedia containers, and deploying network segmentation to limit exposure of systems processing untrusted content. Organizations should also consider implementing sandboxing mechanisms and runtime monitoring to detect and prevent exploitation attempts.
The vulnerability highlights the importance of consistent data validation across all components of multimedia processing frameworks and demonstrates how seemingly minor inconsistencies in container parsing can lead to catastrophic security failures. This flaw serves as a reminder of the critical need for comprehensive testing of edge cases in multimedia processing systems, particularly when dealing with complex container formats that require careful parsing and validation of metadata structures. The exploitation of this vulnerability underscores the necessity for robust error handling and input sanitization in multimedia libraries, as well as the importance of maintaining consistent internal state management across different processing components within media frameworks.