CVE-2015-8790 in libEBML
Summary
by MITRE
The EbmlUnicodeString::UpdateFromUTF8 function in libEBML before 1.3.3 allows context-dependent attackers to obtain sensitive information from process heap memory via a crafted UTF-8 string, which triggers an invalid memory access.
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Analysis
by VulDB Data Team • 07/06/2022
The vulnerability identified as CVE-2015-8790 resides within the libEBML library, a critical component used for handling EBML (Extensible Binary Meta Language) formatted files commonly found in multimedia applications such as matroska containers. This library serves as the foundation for parsing and generating binary metadata structures that are essential for media file handling across numerous software platforms. The specific flaw manifests in the EbmlUnicodeString::UpdateFromUTF8 function, which processes UTF-8 encoded strings during the conversion from UTF-8 to internal Unicode representations. This function operates as a bridge between different text encoding standards within the multimedia processing pipeline, making it a crucial element in the software's data handling architecture.
The technical nature of this vulnerability stems from improper memory management during UTF-8 string processing, specifically when the UpdateFromUTF8 function encounters malformed or crafted input sequences. When an attacker provides a specially constructed UTF-8 string, the function fails to properly validate memory boundaries during the conversion process, leading to what is classified as an information disclosure vulnerability. This flaw operates under the context-dependent attack model where the malicious input must be processed by the vulnerable library in a specific operational environment. The vulnerability is categorized under CWE-125 as an "Out-of-bounds Read" condition, where the function attempts to access memory locations beyond the allocated buffer boundaries, potentially exposing sensitive heap memory contents to unauthorized parties.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially allow attackers to extract sensitive data from process memory, including cryptographic keys, user credentials, or other confidential information stored in adjacent memory locations. This type of vulnerability is particularly dangerous in multimedia processing environments where the library may be processing untrusted input from various sources such as user-uploaded media files or network streams. The vulnerability affects systems that utilize libEBML versions prior to 1.3.3, which represents a significant portion of legacy software installations that may not have received timely security updates. Attackers can leverage this vulnerability through the ATT&CK technique of "Exploitation for Data Exfiltration" by crafting malicious UTF-8 sequences that trigger the memory access violation, thereby enabling them to harvest sensitive information from the heap memory space.
Mitigation strategies for CVE-2015-8790 primarily focus on upgrading to libEBML version 1.3.3 or later, which contains the necessary patches to properly handle memory boundaries during UTF-8 string processing. System administrators should prioritize patch management across all affected applications that utilize the vulnerable library, particularly in enterprise environments where multimedia processing is prevalent. Additional defensive measures include implementing input validation mechanisms that sanitize UTF-8 sequences before they reach the vulnerable function, deploying memory protection techniques such as address space layout randomization, and utilizing security monitoring tools that can detect anomalous memory access patterns. The vulnerability also underscores the importance of proper software supply chain security practices, as this type of flaw demonstrates how seemingly benign library functions can become attack vectors when memory management is not properly implemented. Organizations should consider implementing automated vulnerability scanning tools that can identify outdated library versions and ensure that all multimedia processing applications maintain current security patches to prevent exploitation of similar memory corruption vulnerabilities.