CVE-2016-1515 in libEBML
Summary
by MITRE
A use-after-free / double-free vulnerability can occur in libebml master branch while parsing Track elements of the MKV container.
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Analysis
by VulDB Data Team • 07/15/2020
The vulnerability identified as CVE-2016-1515 represents a critical memory safety issue within the libebml library, which serves as a foundational component for parsing matroska container format files. This library is widely utilized across various multimedia applications and systems for handling mkv files, making the vulnerability particularly concerning from a security perspective. The flaw manifests specifically during the parsing of Track elements within the mkv container structure, where improper memory management leads to potential exploitation by malicious actors. The vulnerability affects the master branch of libebml, indicating it was present in the development version prior to any patches or fixes being implemented. This type of memory corruption vulnerability can have far-reaching implications for systems that rely on proper parsing of multimedia content, as it creates opportunities for arbitrary code execution or system instability.
The technical nature of this vulnerability stems from a use-after-free condition combined with a potential double-free scenario that occurs during the processing of Track elements in mkv files. When the libebml library encounters malformed or specially crafted Track elements within an mkv container, it fails to properly manage memory allocation and deallocation sequences. This improper memory handling creates situations where pointers may be accessed after the memory they reference has been freed, or where the same memory location might be freed twice. Such conditions are classic indicators of memory safety vulnerabilities that can be exploited through carefully crafted input data to manipulate program execution flow. The vulnerability specifically targets the parsing logic within the library's handling of track information, which includes metadata about audio and video streams within the container format. The flaw demonstrates poor resource management practices that violate fundamental principles of secure coding and memory safety.
The operational impact of CVE-2016-1515 extends beyond simple system crashes or instability, as it creates potential pathways for remote code execution in affected systems. When multimedia applications process maliciously crafted mkv files containing specially constructed Track elements, the vulnerable libebml library can be forced into executing arbitrary code with the privileges of the affected application. This makes the vulnerability particularly dangerous in environments where users might encounter untrusted multimedia content, such as web browsers, media players, or content processing systems. The attack surface is broad due to the widespread adoption of the libebml library across different software platforms, meaning that exploitation could affect numerous applications that depend on this parsing library. System administrators and security professionals must consider that exploitation of this vulnerability could lead to complete system compromise, especially when applications using libebml run with elevated privileges or handle content from untrusted sources.
Mitigation strategies for this vulnerability require immediate attention from system administrators and software maintainers. The primary solution involves updating to patched versions of the libebml library where the memory management issues have been resolved through proper implementation of memory allocation and deallocation routines. Organizations should conduct thorough inventory assessments to identify all systems and applications that depend on the vulnerable library version. Additionally, implementing input validation and sanitization measures can help reduce the attack surface by filtering out malformed mkv content before it reaches the vulnerable parsing code. Network-level protections such as content filtering and sandboxing mechanisms can provide additional layers of defense. From a compliance perspective, this vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions, and may also relate to CWE-764 for improper resource management. The vulnerability could potentially map to ATT&CK technique T1059.007 for command and scripting interpreter execution, as successful exploitation might enable attackers to execute arbitrary commands through the compromised application. Regular security assessments and vulnerability management programs should include monitoring for similar memory safety issues in other multimedia processing libraries to prevent analogous vulnerabilities from being exploited in the future.