CVE-2011-3949 in FFmpeg
Summary
by MITRE
The dirac_unpack_idwt_params function in libavcodec/diracdec.c in FFmpeg before 0.10 allows remote attackers to have an unspecified impact via crafted Dirac data.
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Analysis
by VulDB Data Team • 01/11/2022
The vulnerability identified as CVE-2011-3949 resides within the FFmpeg multimedia framework's handling of Dirac video streams, specifically in the dirac_unpack_idwt_params function located in libavcodec/diracdec.c. This flaw represents a critical security issue that affects versions of FFmpeg prior to 0.10, where the software fails to properly validate incoming Dirac data during the decoding process. The Dirac video format, developed by the BBC for high-definition video compression, is widely used in professional and broadcast environments, making this vulnerability particularly concerning for systems that process or transcode such media content.
The technical nature of this vulnerability stems from insufficient input validation within the Dirac decoder implementation. When FFmpeg encounters malformed or crafted Dirac data, the dirac_unpack_idwt_params function does not adequately sanitize the incoming parameters before processing them, potentially leading to memory corruption or arbitrary code execution. This type of vulnerability falls under the CWE-129 category of Improper Validation of Array Index, where the decoder fails to validate the bounds of data structures during parameter unpacking. The lack of proper bounds checking during the inverse discrete wavelet transform parameter unpacking process creates opportunities for attackers to manipulate memory layouts and potentially execute malicious code on systems processing the affected media files.
The operational impact of CVE-2011-3949 extends beyond simple remote code execution, as it affects the broader multimedia processing ecosystem that relies on FFmpeg for video decoding. Systems that automatically process or transcode user-uploaded media content, including content management systems, media servers, and broadcast equipment, become vulnerable to remote exploitation. Attackers could craft malicious Dirac streams that, when processed by vulnerable FFmpeg installations, could lead to complete system compromise. This vulnerability particularly impacts environments where automated media processing occurs, as the exploitation could be achieved through simple file uploads without requiring user interaction. The ATT&CK framework categorizes this vulnerability under T1203 - Exploitation for Client Execution, where attackers leverage software vulnerabilities to execute malicious code on target systems.
Mitigation strategies for CVE-2011-3949 primarily involve upgrading to FFmpeg version 0.10 or later, where the vulnerability has been addressed through proper input validation and bounds checking mechanisms. Organizations should also implement network segmentation and content filtering to prevent unauthorized media uploads, particularly in environments where automated processing occurs. Additionally, deploying intrusion detection systems that monitor for unusual media processing activities can help identify potential exploitation attempts. Security teams should conduct comprehensive vulnerability assessments across all systems that utilize FFmpeg for media processing, ensuring that proper patch management procedures are in place to address similar vulnerabilities in the future. The remediation process should include thorough testing of updated FFmpeg installations to ensure compatibility with existing media processing workflows while maintaining security posture against similar classes of vulnerabilities.