CVE-2016-1514 in libEBML
Summary
by MITRE
A specially crafted unicode string in libebml master branch can cause an off-by-few read on the heap in unicode string parsing code in libebml. This issue can potentially be used for information leaks.
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Analysis
by VulDB Data Team • 10/27/2022
The vulnerability identified as CVE-2016-1514 resides within the libebml library, a critical component used for parsing EBML (Extensible Binary Meta Language) formatted files commonly found in multimedia applications such as matroska containers. This library serves as a foundational element in various media processing systems including video players, editors, and streaming platforms that rely on proper EBML parsing for file handling. The flaw manifests specifically within the unicode string parsing functionality where the library fails to properly validate input data lengths during character sequence processing. This vulnerability falls under the category of memory safety issues and is classified as a heap-based buffer over-read condition that occurs when processing specially crafted unicode sequences.
The technical implementation of this vulnerability involves a precise manipulation of unicode character data that causes the parsing code to read beyond the allocated memory boundaries. When the libebml library encounters a malformed unicode string, the parsing routine executes an off-by-few read operation where it accesses heap memory locations that are not properly accounted for in the intended buffer size calculations. This particular issue stems from inadequate boundary checking within the unicode parsing algorithm, allowing an attacker to craft input that triggers memory access violations. The vulnerability demonstrates characteristics consistent with CWE-125, which describes out-of-bounds read conditions in memory management, and specifically relates to heap-based memory corruption scenarios where the attacker can influence the amount of memory accessed beyond intended boundaries.
The operational impact of CVE-2016-1514 extends beyond simple information disclosure to potentially enable more sophisticated exploitation techniques. While the primary concern is information leak through heap memory exposure, this vulnerability could serve as a stepping stone for more advanced attacks such as remote code execution or privilege escalation depending on the target system architecture and memory layout. The vulnerability affects systems that process EBML formatted files through the libebml library, which encompasses a wide range of multimedia applications and services including media players, content delivery systems, and streaming servers. Attackers can exploit this issue by crafting malicious EBML files containing specially constructed unicode strings that trigger the heap over-read condition during parsing operations, potentially exposing sensitive memory contents including stack canaries, heap metadata, or other system information.
Mitigation strategies for this vulnerability require immediate patching of affected libebml versions and implementation of robust input validation measures within applications that utilize this library. System administrators should prioritize updating to patched versions of libebml that address the unicode parsing boundary conditions and implement proper memory access controls during file processing operations. The recommended approach includes deploying defensive programming practices such as bounds checking, input sanitization, and memory access validation that prevent unauthorized memory reads. Additionally, organizations should consider implementing application sandboxing and privilege separation techniques to limit the potential impact of successful exploitation attempts. Security monitoring should include detection of malformed EBML file processing activities and implementation of intrusion detection systems capable of identifying suspicious unicode string patterns that may indicate exploitation attempts. This vulnerability highlights the importance of proper memory management in multimedia processing libraries and demonstrates how seemingly minor parsing issues can result in significant security implications across a broad spectrum of affected applications and services.