CVE-2017-14223 in FFmpeg
Summary
by MITRE
In libavformat/asfdec_f.c in FFmpeg 3.3.3, a DoS in asf_build_simple_index() due to lack of an EOF (End of File) check might cause huge CPU consumption. When a crafted ASF file, which claims a large "ict" field in the header but does not contain sufficient backing data, is provided, the for loop would consume huge CPU and memory resources, since there is no EOF check inside the loop.
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Analysis
by VulDB Data Team • 12/28/2022
The vulnerability CVE-2017-14223 represents a critical denial of service flaw within the FFmpeg multimedia framework, specifically in the ASF (Advanced Systems Format) demultiplexer component. This issue resides in the libavformat/asfdec_f.c file and affects FFmpeg version 3.3.3, making it a significant concern for systems that process ASF media files. The flaw stems from inadequate input validation and boundary checking mechanisms that fail to properly verify file integrity before processing potentially malicious content. The vulnerability manifests when a crafted ASF file attempts to exploit a mismatch between the declared data size in the file header and the actual available data, creating a scenario where the software enters into resource-intensive processing loops without proper termination conditions.
The technical implementation of this vulnerability occurs within the asf_build_simple_index() function where the software processes the "ict" field from the ASF file header. This field typically indicates the number of index entries that should be processed, but when maliciously inflated without corresponding data, it triggers an unbounded loop execution. The absence of end-of-file checks within the processing loop allows the software to continue iterating based on the inflated count value, consuming excessive CPU cycles and memory resources. This behavior directly violates security principles and can be classified under CWE-129 Input Validation and Output Range Checking, specifically addressing improper validation of input data ranges. The flaw demonstrates a classic case of insufficient resource management where the software fails to implement proper bounds checking mechanisms to prevent excessive resource consumption.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by attackers to perform resource exhaustion attacks against systems processing ASF media files. When a maliciously crafted ASF file is processed, the affected software becomes trapped in an infinite loop consuming CPU resources at an exponential rate, potentially leading to system instability or complete denial of service for legitimate users. The vulnerability is particularly concerning in server environments where FFmpeg is used for media processing, transcoding, or streaming services, as attackers could leverage this flaw to overwhelm system resources and disrupt critical operations. The attack vector requires minimal sophistication as it only requires crafting a specific ASF file with manipulated header values, making it a significant threat in automated exploitation scenarios. This vulnerability aligns with ATT&CK technique T1499.004 Resource Hijacking by consuming excessive computational resources to deny service to legitimate users.
Mitigation strategies for CVE-2017-14223 should focus on implementing proper bounds checking and input validation mechanisms within the FFmpeg codebase. The most effective approach involves adding comprehensive end-of-file checks within the processing loops to ensure that the software does not proceed beyond available data boundaries. System administrators should prioritize updating FFmpeg installations to versions that contain the patched implementation, as the vulnerability has been addressed in subsequent releases. Additionally, implementing rate limiting and resource monitoring mechanisms can help detect and prevent exploitation attempts by identifying abnormal CPU and memory usage patterns. Organizations should also consider implementing content filtering and sandboxing techniques for processing untrusted media files to prevent direct exploitation of such vulnerabilities in production environments. The fix typically involves modifying the asf_build_simple_index() function to validate data availability before entering processing loops, ensuring that the software terminates gracefully when insufficient data is present to satisfy header declarations.