CVE-2018-15822 in FFmpeg
Summary
by MITRE
The flv_write_packet function in libavformat/flvenc.c in FFmpeg through 4.0.2 does not check for an empty audio packet, leading to an assertion failure.
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Analysis
by VulDB Data Team • 05/04/2023
The vulnerability identified as CVE-2018-15822 resides within the FFmpeg multimedia framework, specifically in the flv_write_packet function located in libavformat/flvenc.c. This issue affects FFmpeg versions through 4.0.2 and represents a critical flaw in the handling of audio packets during FLV (Flash Video) file encoding operations. The vulnerability stems from the absence of proper validation checks for audio packet content, creating a scenario where empty audio packets can be processed without adequate verification. This fundamental oversight in input validation creates a condition that can lead to system instability and potential denial of service scenarios.
The technical implementation of this vulnerability manifests through the assertion failure that occurs when the flv_write_packet function encounters an empty audio packet. Assertions are typically used during development to catch programming errors and invalid conditions, but when these assertions fail in production code, they can cause the application to terminate unexpectedly. The flaw specifically occurs because the function does not perform a null or empty packet check before attempting to process audio data, which violates standard input validation practices. This type of vulnerability falls under CWE-457: Use of Uninitialized Variable, as the function operates on potentially uninitialized or empty audio packet data without proper safeguards.
From an operational perspective, this vulnerability presents significant risks to systems that rely on FFmpeg for video processing and encoding tasks. Attackers could potentially exploit this weakness by crafting malicious FLV files or manipulating audio streams to trigger the assertion failure, leading to application crashes or denial of service conditions. The impact extends beyond simple service interruption, as this vulnerability could be leveraged in broader attack chains where multiple system components depend on FFmpeg for media processing. The vulnerability affects various applications that utilize FFmpeg as a backend library for video encoding, including content management systems, streaming platforms, and media processing pipelines. This weakness aligns with ATT&CK technique T1499.004: Endpoint Denial of Service, as it specifically targets the availability of media processing services through assertion failures.
The mitigation strategy for CVE-2018-15822 involves immediate patching of FFmpeg installations to versions that address this specific assertion failure. System administrators should prioritize updating their FFmpeg libraries to versions 4.0.3 or later, where the empty audio packet validation has been implemented. Additionally, implementing proper input validation at the application level that wraps FFmpeg functionality can provide an additional layer of protection against malformed audio packets. Organizations should also consider deploying intrusion detection systems that can monitor for unusual assertion failures or application crashes related to media processing functions. The fix implemented in the patched versions typically involves adding explicit checks for empty audio packets before processing, ensuring that the function gracefully handles edge cases rather than failing with assertion errors. This vulnerability demonstrates the importance of comprehensive input validation and proper error handling in multimedia processing libraries, as the absence of such checks can lead to system instability and potential exploitation by malicious actors.