CVE-2009-4634 in FFmpeg
Summary
by MITRE
Multiple integer underflows in FFmpeg 0.5 allow remote attackers to cause a denial of service and possibly execute arbitrary code via a crafted file that (1) bypasses a validation check in vorbis_dec.c and triggers a wraparound of the stack pointer, or (2) access a pointer from out-of-bounds memory in mov.c, related to an elst tag that appears before a tag that creates a stream.
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Analysis
by VulDB Data Team • 04/30/2026
The vulnerability described in CVE-2009-4634 represents a critical security flaw in FFmpeg version 0.5 that exposes the multimedia processing library to remote code execution and denial of service attacks. This vulnerability stems from multiple integer underflow conditions that occur during the processing of specially crafted media files, making it particularly dangerous for systems that handle untrusted multimedia content. The flaw affects the core decoding functionality of FFmpeg, which is widely used across various platforms and applications for multimedia processing, creating a significant attack surface for malicious actors.
The technical implementation of this vulnerability manifests through two distinct attack vectors that exploit different components within the FFmpeg codebase. The first vector involves a validation check bypass in vorbis_dec.c that leads to stack pointer wraparound when processing crafted vorbis audio files, while the second vector targets mov.c through improper handling of elst tags that appear before stream creation tags in mov files. Both scenarios result from insufficient input validation and improper integer overflow/underflow checks during the parsing of multimedia metadata. These conditions create predictable memory corruption scenarios that can be exploited by attackers to manipulate program execution flow. The underlying issue aligns with CWE-191, which specifically addresses integer underflow conditions, and represents a classic example of how improper input validation can lead to memory corruption vulnerabilities.
The operational impact of CVE-2009-4634 extends beyond simple denial of service to potentially enable remote code execution, making it particularly dangerous in environments where FFmpeg processes untrusted content. Attackers can leverage these vulnerabilities in web applications, media servers, or any system that utilizes FFmpeg for multimedia processing without proper input sanitization. The vulnerability's exploitation requires crafting specific malicious files that trigger the integer underflow conditions, but once successful, the consequences can be severe including complete system compromise. This vulnerability directly relates to ATT&CK technique T1203, which covers legitimate program execution through the use of command and scripting interpreter, and T1059, covering command and scripting interpreter. The attack surface is extensive given FFmpeg's widespread adoption in media processing pipelines, streaming servers, content management systems, and various multimedia applications, making it a prime target for attackers seeking to compromise systems through multimedia content delivery.
Mitigation strategies for CVE-2009-4634 should focus on immediate patching of FFmpeg installations to versions that address the identified integer underflow conditions. Organizations must implement comprehensive input validation and sanitization procedures for all multimedia content processed through FFmpeg, particularly when handling untrusted files from external sources. Network segmentation and content filtering mechanisms should be deployed to prevent unauthorized access to systems that process multimedia files. Additionally, regular security assessments and vulnerability scanning should be conducted to identify and remediate similar issues in other multimedia processing libraries and components. The vulnerability demonstrates the critical importance of proper integer handling in security-sensitive applications and reinforces the need for comprehensive code review processes that specifically address integer overflow and underflow conditions as outlined in industry best practices for secure coding standards.