CVE-2017-12781 in libebml2
Summary
by MITRE
The EBML_BufferToID function in ebmlelement.c in libebml2 through 2012-08-26 allows remote attackers to cause a denial of service (Null pointer dereference and application crash) via a crafted mkv file.
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Analysis
by VulDB Data Team • 01/10/2023
The vulnerability identified as CVE-2017-12781 affects libebml2, a library used for parsing and writing Extensible Binary Meta Language files commonly associated with matroska multimedia formats. This flaw exists within the EBML_BufferToID function located in the ebmlelement.c source file, representing a critical security issue that enables remote attackers to execute denial of service attacks against systems processing mkv media files. The vulnerability specifically manifests when the library encounters malformed or crafted mkv files that trigger a null pointer dereference condition during the parsing process.
The technical implementation of this vulnerability stems from insufficient input validation within the EBML_BufferToID function which fails to properly handle malformed buffer data structures. When processing a specially crafted mkv file, the function attempts to dereference a null pointer, leading to an application crash and complete service disruption. This behavior aligns with CWE-476, which categorizes null pointer dereference vulnerabilities as a common weakness in software security implementations. The flaw demonstrates a classic buffer handling error where the code assumes certain data structures will contain valid references without proper validation checks.
From an operational perspective, this vulnerability presents significant risks to multimedia processing systems, streaming services, and content management platforms that rely on libebml2 for handling matroska format files. Attackers can exploit this weakness by simply preparing a malicious mkv file and presenting it to a vulnerable system, requiring no specialized privileges or complex attack vectors. The impact extends beyond simple service disruption to potentially affect availability of multimedia services, content delivery networks, and user experience in applications that process video and audio files. This vulnerability particularly affects systems that automatically process or validate user-uploaded media files without proper sanitization mechanisms.
Organizations should implement immediate mitigations including updating to the latest version of libebml2 where the vulnerability has been patched, implementing input validation controls for all media file processing, and deploying automated scanning systems to detect and quarantine potentially malicious media files. The fix typically involves adding proper null pointer checks within the EBML_BufferToID function to prevent the dereference operation when buffer data is invalid or incomplete. Additionally, system administrators should consider implementing network-level filtering rules to prevent unauthorized access to vulnerable systems and establish monitoring protocols to detect potential exploitation attempts. This vulnerability also highlights the importance of following secure coding practices and adhering to ATT&CK framework principles for preventing remote code execution and denial of service conditions in multimedia processing environments.