CVE-2011-3940 in FFmpeg
Summary
by MITRE
nsvdec.c in libavcodec in FFmpeg 0.7.x before 0.7.12 and 0.8.x before 0.8.11, and in Libav 0.5.x before 0.5.9, 0.6.x before 0.6.6, 0.7.x before 0.7.5, and 0.8.x before 0.8.1, allows remote attackers to cause a denial of service (out-of-bounds read and write) via a crafted NSV file that triggers "use of uninitialized streams."
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/08/2021
The vulnerability described in CVE-2011-3940 represents a critical memory corruption flaw affecting multimedia processing libraries used extensively across various software applications. This issue resides within the nsvdec.c component of FFmpeg and Libav libraries, which are fundamental building blocks for video and audio decoding in countless media players, streaming applications, and content processing systems. The flaw manifests when these libraries process specially crafted NSV (Netscape Streaming Video) files that contain malformed data structures, leading to unpredictable behavior in the underlying memory management systems.
The technical root cause of this vulnerability stems from improper handling of uninitialized memory streams during the decoding process. When an attacker crafts an NSV file with specific malformed parameters, the nsvdec.c decoder fails to properly validate input data before using it in memory operations. This results in out-of-bounds read and write operations that can corrupt adjacent memory regions or cause the application to crash entirely. The vulnerability specifically targets the initialization sequence of stream data structures, where the decoder attempts to access memory locations that have not been properly allocated or initialized, creating a dangerous condition that can be exploited remotely.
The operational impact of this vulnerability extends far beyond simple denial of service, as it can potentially enable more sophisticated attacks depending on the target application's execution environment. When exploited successfully, the out-of-bounds memory operations can cause applications using these libraries to crash, leading to service disruption for end users. However, the more concerning aspect is that such memory corruption vulnerabilities often serve as stepping stones for more advanced exploitation techniques, including potential code execution attacks. The vulnerability affects multiple versions of both FFmpeg and Libav, indicating it was present across several release branches and likely impacted a substantial portion of the multimedia software ecosystem.
Organizations and developers should prioritize immediate mitigation through library updates to versions that contain patches addressing this vulnerability. The affected versions include FFmpeg 0.7.x before 0.7.12 and 0.8.x before 0.8.11, as well as various Libav versions spanning from 0.5.x through 0.8.x releases. System administrators should implement comprehensive patch management procedures to ensure all applications utilizing these multimedia libraries are updated promptly. Additionally, input validation measures should be enhanced at application layers that process user-supplied media files, implementing strict file format validation and sandboxing techniques to prevent exploitation attempts.
This vulnerability aligns with CWE-457: Use of Uninitialized Variable, which specifically addresses the dangerous practice of using variables without proper initialization, creating potential security risks. From an ATT&CK perspective, this issue falls under the category of privilege escalation through software exploitation, as it allows remote attackers to compromise systems through media processing components. The vulnerability demonstrates how multimedia libraries, which are often considered core system components, can contain critical security flaws that impact the entire software ecosystem relying on them, making proper vulnerability management and timely patch deployment essential for maintaining system integrity.