CVE-2013-7021 in FFmpeg
Summary
by MITRE
The filter_frame function in libavfilter/vf_fps.c in FFmpeg before 2.1 does not properly ensure the availability of FIFO content, which allows remote attackers to cause a denial of service (double free) or possibly have unspecified other impact via crafted data.
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Analysis
by VulDB Data Team • 01/11/2022
The vulnerability identified as CVE-2013-7021 resides within the FFmpeg multimedia framework, specifically in the libavfilter module's filter_frame function located in vf_fps.c. This flaw represents a critical security issue that affects versions of FFmpeg prior to 2.1, where the software fails to properly validate FIFO content availability during frame processing operations. The vulnerability manifests when FFmpeg processes crafted multimedia data through its filtering pipeline, particularly when handling frame rate conversion operations. The root cause lies in insufficient input validation and memory management practices within the frame filtering mechanism, creating a scenario where malformed data can trigger unexpected behavior in the underlying memory allocation system.
The technical exploitation of this vulnerability occurs through a double free condition that arises when the filter_frame function attempts to process frame data without adequate verification of FIFO buffer states. When maliciously crafted multimedia content is fed into FFmpeg's frame rate conversion filter, the function fails to properly check whether FIFO buffers contain valid data before attempting memory operations. This improper handling can lead to a situation where the same memory block is freed twice, causing a denial of service condition that crashes the application. The vulnerability classification aligns with CWE-415, which describes improper double free conditions in memory management, and may also relate to CWE-476 which addresses null pointer dereferences. The operational impact extends beyond simple service disruption as the vulnerability could potentially be leveraged for more severe consequences depending on the execution environment and how FFmpeg is integrated into larger systems.
The practical implications of CVE-2013-7021 are significant for organizations relying on FFmpeg for multimedia processing, particularly in environments where user-supplied content is processed without proper sanitization. Attackers can exploit this vulnerability by constructing specially crafted multimedia files that, when processed by vulnerable FFmpeg versions, trigger the double free condition. This creates a reliable denial of service vector that can be used to disrupt services, particularly in web applications, content management systems, or media processing pipelines that depend on FFmpeg. The vulnerability is particularly dangerous in server environments where FFmpeg is used to process user uploads, as it can be exploited through simple file uploads without requiring complex attack vectors or privileged access. According to ATT&CK framework, this vulnerability maps to T1499.004 which covers network denial of service attacks, and T1203 which involves exploitation of software vulnerabilities for privilege escalation or service disruption.
Mitigation strategies for CVE-2013-7021 primarily focus on immediate version updates to FFmpeg 2.1 or later, where the vulnerability has been addressed through improved memory management and input validation in the filter_frame function. Organizations should also implement robust input sanitization measures, including content validation and file format checking, before processing any multimedia content through FFmpeg. Additional protective measures include running FFmpeg in restricted environments with proper memory protection mechanisms and implementing monitoring systems to detect potential exploitation attempts. The fix implemented in FFmpeg 2.1 addresses the root cause by ensuring proper FIFO content availability checks and implementing more robust memory deallocation procedures. Security teams should also consider deploying network-based intrusion detection systems that can identify patterns associated with exploitation attempts targeting this specific vulnerability, particularly in environments where multimedia processing is a core function of the infrastructure.