CVE-2018-3933 in Office Server
Summary
by MITRE
An exploitable out-of-bounds write exists in the Microsoft Word document conversion functionality of the Antenna House Office Server Document Converter version V6.1 Pro MR2 for Linux64 (6,1,2018,0312). A crafted Microsoft Word (DOC) document can lead to an out-of-bounds write, resulting in remote code execution. This vulnerability occurs in the `vbputanld` method.
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Analysis
by VulDB Data Team • 04/06/2023
The vulnerability identified as CVE-2018-3933 represents a critical security flaw within the Antenna House Office Server Document Converter version V6.1 Pro MR2 for Linux64, specifically affecting the conversion of Microsoft Word documents. This issue manifests as an exploitable out-of-bounds write condition that can be triggered through the processing of maliciously crafted DOC files, potentially enabling remote code execution on affected systems. The vulnerability is particularly concerning as it exists within a document conversion utility that is commonly deployed in enterprise environments for automated document processing and transformation tasks. The flaw specifically occurs in the `vbputanld` method, which handles the conversion of certain Word document elements, making it a target for attackers seeking to leverage document processing workflows for system compromise.
The technical implementation of this vulnerability stems from inadequate bounds checking within the document parsing logic of the Antenna House converter. When processing specially crafted Microsoft Word documents, the `vbputanld` method fails to properly validate array indices or buffer boundaries, allowing an attacker to write data beyond the allocated memory space. This out-of-bounds write condition can be carefully constructed to overwrite critical memory locations, including function pointers or return addresses, which enables attackers to redirect program execution flow. The vulnerability is classified under CWE-787, which specifically addresses out-of-bounds write conditions, and represents a direct pathway to privilege escalation and system compromise. The attack vector is particularly dangerous because it leverages the common practice of automated document processing in business environments where users may inadvertently open or process malicious documents through legitimate document conversion workflows.
The operational impact of CVE-2018-3933 extends beyond simple remote code execution, as it can be exploited in various attack scenarios within enterprise networks. Organizations using the Antenna House Office Server Document Converter for automated document processing are at risk of complete system compromise when attackers craft malicious Word documents that exploit this vulnerability. The vulnerability can be triggered through multiple attack vectors including email attachments, web downloads, or file sharing platforms where users may encounter malicious documents. According to ATT&CK framework, this vulnerability maps to T1059 (Command and Scripting Interpreter) and T1203 (Exploitation for Client Execution) techniques, as attackers can leverage the converter to execute arbitrary code on target systems. The impact is particularly severe in environments where document conversion is automated or integrated into larger business processes, as the attack can occur without user interaction, making it an ideal candidate for zero-day exploits.
Mitigation strategies for CVE-2018-3933 should focus on immediate patching of the affected Antenna House Office Server Document Converter software to version V6.1 Pro MR3 or later, which contains the necessary fixes for the bounds checking vulnerabilities. Organizations should also implement network-level controls to restrict access to the document conversion service and limit its exposure to untrusted networks or users. Additional defensive measures include implementing strict document validation policies, deploying sandboxing solutions for document processing, and monitoring for suspicious conversion activities. Security teams should also consider disabling unnecessary document conversion services and restricting the types of documents that can be processed through automated workflows. The vulnerability highlights the importance of proper input validation and bounds checking in document processing libraries, as outlined in industry security standards such as the OWASP Top Ten and NIST Cybersecurity Framework, which emphasize the need for robust validation mechanisms in all document handling components.