CVE-2011-3952 in libav
Summary
by MITRE
The decode_init function in kmvc.c in libavcodec in FFmpeg before 0.10 and in Libav 0.5.x before 0.5.9, 0.6.x before 0.6.6, 0.7.x before 0.7.6, and 0.8.x before 0.8.1 allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via a large palette size in a KMVC encoded file.
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Analysis
by VulDB Data Team • 12/08/2021
The vulnerability described in CVE-2011-3952 represents a critical security flaw affecting multimedia processing libraries used extensively across various software applications. This issue resides within the decode_init function of kmvc.c in FFmpeg's libavcodec component, impacting versions prior to specific security patches. The vulnerability stems from inadequate input validation mechanisms that fail to properly handle malformed palette size parameters within KMVC encoded files, creating a pathway for malicious actors to exploit the system through carefully crafted media files.
The technical implementation of this vulnerability involves a buffer overflow condition that occurs when the decode_init function processes KMVC encoded files containing excessively large palette size values. This flaw falls under the CWE-121 category of Stack-based Buffer Overflow, where insufficient bounds checking allows attackers to write beyond allocated memory boundaries. The KMVC (Karl M. V. C.) format is a proprietary video encoding scheme that utilizes palette-based compression techniques, making the palette size parameter particularly critical for proper decoding operations. When an attacker provides a maliciously large palette size value, the function attempts to allocate memory based on this oversized parameter, leading to memory corruption that can result in application crashes or potentially arbitrary code execution.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can enable remote code execution in vulnerable applications that process KMVC encoded media files. This represents a significant threat vector since KMVC files are commonly encountered in multimedia applications, web browsers, and media processing software. The vulnerability affects a wide range of software systems including media players, content management systems, and web applications that rely on FFmpeg or Libav libraries for video processing. Attackers can leverage this weakness by embedding malicious KMVC files in web content, email attachments, or file sharing systems, potentially compromising systems when users view or process these files through vulnerable applications.
The exploitation of this vulnerability aligns with several ATT&CK tactics including Execution through legitimate system binaries and Defense Evasion by leveraging existing multimedia processing capabilities. The attack surface is particularly broad given that FFmpeg and Libav are foundational components in numerous software ecosystems, including major browsers, media players, and server applications. Organizations using affected versions of these libraries face significant risk exposure, as the vulnerability can be triggered through common user interactions with multimedia content. The potential for remote code execution makes this particularly dangerous in environments where users may encounter untrusted media files, such as in web browsing or email processing scenarios.
Mitigation strategies for CVE-2011-3952 require immediate patching of affected software components to ensure proper bounds checking and memory allocation handling. System administrators should prioritize updating FFmpeg and Libav installations to versions containing the necessary security fixes, particularly focusing on the specific version ranges mentioned in the vulnerability description. Additional protective measures include implementing content filtering mechanisms that scan multimedia files for suspicious palette size parameters, deploying network-based intrusion detection systems to monitor for exploitation attempts, and establishing secure coding practices that enforce strict input validation for all multimedia processing components. Organizations should also consider implementing application whitelisting policies and sandboxing techniques to limit the potential impact of successful exploitation attempts, while maintaining comprehensive monitoring and incident response procedures to detect and respond to any exploitation attempts.