CVE-2017-12802 in libEBML
Summary
by MITRE
The EBML_IntegerValue function in ebmlnumber.c in libebml2 through 2012-08-26 allows remote attackers to cause a denial of service (assert fault) via a crafted mkv file.
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Analysis
by VulDB Data Team • 01/10/2023
The vulnerability identified as CVE-2017-12802 resides within the libebml2 library, specifically in the EBML_IntegerValue function located in ebmlnumber.c. This library serves as a core component for handling Extensible Binary Meta Language files, which are fundamental to the matroska multimedia container format commonly used in video and audio streaming applications. The flaw manifests when processing malformed mkv files that contain crafted integer values, leading to an assertion failure that terminates the application process. This represents a classic denial of service vulnerability that can be exploited by remote attackers without requiring any special privileges or authentication.
The technical implementation of this vulnerability stems from inadequate input validation within the EBML_IntegerValue function, which fails to properly handle malformed integer encodings in the binary data structure. When a maliciously crafted mkv file is processed, the function encounters an unexpected integer value that triggers an assertion check, causing the application to crash or terminate abruptly. This behavior falls under CWE-691, which specifically addresses insufficient control flow management in software systems. The vulnerability demonstrates poor error handling and input sanitization practices that are commonly exploited in binary format parsing libraries where malformed data can lead to unexpected program termination.
From an operational perspective, this vulnerability poses significant risks to applications that rely on libebml2 for processing multimedia content, particularly those handling untrusted user uploads or streaming content from external sources. The denial of service impact can be severe for streaming services, content delivery networks, or media processing applications that may experience complete service interruption when processing maliciously crafted files. Attackers can exploit this vulnerability by simply providing a specially crafted mkv file that triggers the assertion failure, making it a particularly dangerous flaw for systems handling user-generated content or third-party media files. The vulnerability affects all versions of libebml2 up to and including the 2012-08-26 release, indicating a long-standing issue that remained unpatched for an extended period.
The exploitation of this vulnerability aligns with ATT&CK technique T1499.004, which focuses on network denial of service attacks through application-level flaws. Organizations using affected software should implement immediate mitigations including input validation, file format sanitization, and application sandboxing to prevent exploitation. The recommended approach involves updating to patched versions of libebml2, implementing proper error handling mechanisms, and deploying content filtering systems that can detect and reject potentially malicious media files before they reach the processing layer. Additionally, system administrators should consider implementing network segmentation and monitoring solutions to detect potential exploitation attempts and maintain audit trails for forensic analysis. This vulnerability serves as a reminder of the critical importance of robust input validation in multimedia processing libraries and the potential for seemingly minor flaws to create significant operational disruptions.