CVE-2017-14056 in FFmpeg
Summary
by MITRE
In libavformat/rl2.c in FFmpeg 3.3.3, a DoS in rl2_read_header() due to lack of an EOF (End of File) check might cause huge CPU and memory consumption. When a crafted RL2 file, which claims a large "frame_count" field in the header but does not contain sufficient backing data, is provided, the loops (for offset and size tables) would consume huge CPU and memory resources, since there is no EOF check inside these loops.
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Analysis
by VulDB Data Team • 12/27/2022
The vulnerability CVE-2017-14056 represents a critical denial of service weakness in FFmpeg's rl2.c component, specifically within the rl2_read_header() function. This flaw exists in version 3.3.3 of the multimedia framework and demonstrates a classic lack of input validation that can be exploited to consume excessive system resources. The issue stems from insufficient end-of-file boundary checking during the processing of RL2 video files, which are commonly used in various multimedia applications and games. The vulnerability manifests when a maliciously crafted RL2 file contains an inflated frame_count field in its header structure, creating a scenario where the parser enters resource-intensive loops without proper termination conditions.
The technical exploitation of this vulnerability occurs through the manipulation of the frame_count field within the RL2 file header, which serves as a loop counter for processing offset and size tables. When the parser encounters a crafted file with an artificially large frame_count value, it initiates loops that iterate based on this inflated number rather than actual file content. These loops operate without proper EOF checks, causing the system to allocate substantial memory resources and consume excessive CPU cycles as it attempts to process non-existent data. The absence of boundary validation allows the parser to continue processing beyond the actual file boundaries, leading to unbounded resource consumption that can effectively crash or render the application unresponsive.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged by attackers to consume system resources and potentially cause system instability or performance degradation. The vulnerability affects any application that utilizes FFmpeg's rl2.c component for processing RL2 video files, including multimedia players, video editing software, and streaming applications. This weakness is particularly concerning in server environments where FFmpeg is used for media processing, as it could be exploited to exhaust system resources and cause legitimate services to become unavailable. The vulnerability aligns with CWE-129, which addresses improper validation of the length of input data, and demonstrates characteristics consistent with attack patterns described in the MITRE ATT&CK framework under the T1499.004 technique for network denial of service.
Mitigation strategies for CVE-2017-14056 should focus on implementing robust input validation and boundary checking within the rl2_read_header() function. The most effective approach involves adding proper EOF checks within the loops that process frame data, ensuring that the parser verifies available file content before proceeding with resource-intensive operations. System administrators should update to FFmpeg versions that contain the patched rl2.c implementation, which typically includes bounds checking and input validation mechanisms. Additionally, organizations should implement input sanitization measures and consider deploying network monitoring tools to detect unusual resource consumption patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the importance of defensive programming practices and proper resource management in multimedia processing libraries, particularly when handling potentially malformed input files from untrusted sources.