CVE-2017-18242 in libav
Summary
by MITRE
The apply_dependent_coupling function in libavcodec/aacdec.c in Libav 12.2 allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted aac file.
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Analysis
by VulDB Data Team • 01/15/2020
The vulnerability identified as CVE-2017-18242 resides within the Libav multimedia framework, specifically in the AAC audio decoding component located at libavcodec/aacdec.c. This flaw manifests in the apply_dependent_coupling function which processes audio data during AAC file decoding operations. The issue represents a classic out-of-bounds read vulnerability that can be exploited by remote attackers through the careful crafting of malicious AAC files. Such vulnerabilities are particularly dangerous in multimedia processing libraries as they can be triggered during normal playback operations, making them attractive targets for attackers seeking to disrupt services or potentially execute arbitrary code.
The technical nature of this vulnerability stems from insufficient input validation within the audio decoding pipeline. When the apply_dependent_coupling function processes AAC audio data, it fails to properly bounds-check array access operations that occur during dependent coupling calculations. This allows an attacker to construct an AAC file with malformed data that causes the decoder to read memory locations beyond the allocated buffer boundaries. The out-of-bounds read can result in unpredictable behavior including program crashes, data corruption, or in some cases, information disclosure. This vulnerability directly maps to CWE-129, which addresses insufficient bounds checking, and represents a common pattern in multimedia decoding libraries where complex parsing logic fails to validate all input parameters before use.
From an operational impact perspective, this vulnerability creates significant risk for systems that process AAC audio files from untrusted sources. The remote exploitation capability means that attackers can trigger the denial of service condition without requiring local access or user interaction. This makes it particularly dangerous in web applications, media servers, or any system that accepts user-uploaded audio content. The vulnerability can be leveraged to cause persistent service disruption through repeated exploitation attempts, effectively rendering affected systems unavailable to legitimate users. In enterprise environments, this could lead to widespread service degradation across multiple applications that depend on Libav for audio processing capabilities.
Mitigation strategies for CVE-2017-18242 should prioritize immediate patching of affected Libav installations to version 12.3 or later where the vulnerability has been addressed through proper bounds checking implementation. System administrators should also implement input validation measures at network boundaries to filter potentially malicious audio files before they reach processing systems. The ATT&CK framework categorizes this type of vulnerability under T1203, which covers exploitation for privilege escalation, though in this case the impact is primarily denial of service rather than privilege gain. Organizations should also consider implementing application sandboxing techniques to limit the potential impact if exploitation were to succeed, and establish monitoring protocols to detect unusual processing patterns that might indicate exploitation attempts. Regular security assessments of multimedia processing pipelines should be conducted to identify similar vulnerabilities in other components of the audio processing stack.