CVE-2017-18244 in libav
Summary
by MITRE
The stereo_processing function in libavcodec/aacps.c in Libav 12.2 allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted aac file, related to ff_ps_apply.
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Analysis
by VulDB Data Team • 01/15/2020
The vulnerability identified as CVE-2017-18244 resides within the Libav multimedia framework, specifically in the stereo_processing function located in libavcodec/aacps.c. This flaw represents a critical out-of-bounds read condition that can be exploited by remote attackers through the careful crafting of Advanced Audio Coding format files. The vulnerability is particularly concerning because it affects the ff_ps_apply function which handles the processing of psychoacoustic parameters in AAC audio streams, making it a core component of audio decoding operations.
The technical implementation of this vulnerability stems from inadequate input validation within the stereo processing logic. When a maliciously crafted AAC file is processed by Libav's audio decoder, the stereo_processing function fails to properly bounds-check array accesses during the application of psychoacoustic parameters. This allows an attacker to manipulate the audio file structure in such a way that memory locations outside the intended array boundaries are accessed, leading to unpredictable behavior and ultimately resulting in a denial of service condition. The flaw demonstrates characteristics consistent with CWE-129, which addresses improper validation of array indices, and CWE-787, which covers out-of-bounds writes and reads.
The operational impact of this vulnerability extends beyond simple service disruption as it can be leveraged in various attack scenarios including but not limited to web application exploitation, media server compromise, and content delivery network attacks. Any system that processes AAC audio files through Libav, including streaming services, media servers, and content management systems, becomes vulnerable to this attack vector. The remote nature of the exploit means that attackers do not require local system access, making it particularly dangerous for services that accept user-uploaded media content. This vulnerability aligns with ATT&CK technique T1203, which involves legitimate programs that are used for exploitation, and can be classified under the broader category of privilege escalation through software supply chain compromise.
Mitigation strategies for CVE-2017-18244 should prioritize immediate patching of affected Libav installations to version 12.3 or later where the out-of-bounds read has been corrected. Organizations should implement strict input validation for all audio file processing workflows and consider deploying sandboxing mechanisms around media processing components to limit the potential impact of exploitation attempts. Network-based detection measures can be implemented to identify and block suspicious AAC file patterns that may indicate crafted malicious content. Additionally, regular security assessments of multimedia processing pipelines should be conducted to identify similar vulnerabilities in other components of the audio processing stack, ensuring comprehensive protection against similar out-of-bounds access vulnerabilities that could be leveraged for more sophisticated attacks including remote code execution.