CVE-2017-12783 in libEBML
Summary
by MITRE
The ReadDataFloat 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-2017-12783 resides within the libebml2 library, specifically in the ReadDataFloat function located in ebmlnumber.c. This library serves as a core component for handling Extensible Binary Meta Language (EBML) formatted data, which is widely used in multimedia file formats including Matroska (MKV) containers. The flaw manifests when processing maliciously crafted MKV files that contain specially constructed floating-point data, leading to an assertion failure that terminates the application. This vulnerability represents a classic denial of service condition where legitimate users cannot access the service due to the application crashing or becoming unresponsive. The issue affects versions of libebml2 released through August 26, 2012, indicating this was a long-standing problem that remained unpatched for an extended period. The vulnerability is particularly concerning as it allows remote attackers to exploit the flaw without requiring any special privileges or authentication, making it an attractive target for malicious actors seeking to disrupt services.
The technical nature of this vulnerability stems from inadequate input validation within the ReadDataFloat function. When the function processes floating-point data from an EBML structure, it fails to properly validate the data format or bounds before attempting to parse it. This lack of proper validation allows crafted input to trigger an assertion failure, which is a debugging mechanism designed to catch programming errors during development. In production environments, assertions are typically disabled or handled differently, but the presence of malformed data can still cause the application to crash or behave unpredictably. The vulnerability specifically targets the floating-point data parsing logic, suggesting that the function does not adequately handle edge cases or malformed representations of floating-point numbers within the EBML container format. This flaw directly relates to CWE-682, which encompasses incorrect arithmetic operations and improper handling of numeric data types. The assertion failure occurs because the function makes assumptions about the data structure that are violated by malicious input, causing the program to terminate abruptly rather than gracefully handling the error.
The operational impact of CVE-2017-12783 extends beyond simple service disruption to potentially compromise entire multimedia processing pipelines and applications that rely on libebml2 for MKV file handling. Any application that processes MKV files, including media servers, content delivery networks, streaming platforms, and multimedia editing software, becomes vulnerable to this attack vector. The remote exploitation capability means that attackers can trigger the denial of service from anywhere on the network, making it particularly dangerous in web-facing applications or services that accept user-uploaded media files. This vulnerability can be leveraged in various attack scenarios including distributed denial of service campaigns against media servers, or as part of broader exploitation chains where the initial denial of service serves as a precursor to more sophisticated attacks. The vulnerability also demonstrates poor defensive programming practices where error handling and input validation are insufficient to prevent crash conditions. From an attacker perspective, this vulnerability maps to ATT&CK technique T1499.004, which involves network denial of service attacks targeting media services and streaming platforms.
Mitigation strategies for CVE-2017-12783 primarily focus on updating to patched versions of libebml2, as the vulnerability was resolved in subsequent releases. Organizations should implement immediate patch management procedures to upgrade all affected systems and applications that utilize the vulnerable library. Additionally, input validation measures should be implemented at the application level to sanitize MKV files before processing, including implementing proper error handling and recovery mechanisms that prevent assertion failures from terminating applications. Network-based mitigations such as content filtering and file type validation can help prevent malicious MKV files from reaching vulnerable applications. The implementation of defensive programming techniques including bounds checking, proper memory management, and robust error handling should be enforced throughout the codebase to prevent similar vulnerabilities from emerging. Organizations should also consider implementing intrusion detection systems that can identify attempts to exploit this specific vulnerability pattern. Security monitoring and incident response procedures should be updated to include detection and response capabilities for assertion failure-based denial of service attacks, ensuring that administrators can quickly identify and respond to exploitation attempts. Regular security assessments and code reviews should be conducted to identify and remediate similar input validation vulnerabilities in other components of the multimedia processing stack.