CVE-2018-16858 in LibreOffice
Summary
by MITRE
It was found that libreoffice before versions 6.0.7 and 6.1.3 was vulnerable to a directory traversal attack which could be used to execute arbitrary macros bundled with a document. An attacker could craft a document, which when opened by LibreOffice, would execute a Python method from a script in any arbitrary file system location, specified relative to the LibreOffice install location.
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Analysis
by VulDB Data Team • 08/25/2024
The vulnerability identified as CVE-2018-16858 represents a critical directory traversal flaw in LibreOffice versions prior to 6.0.7 and 6.1.3, exposing users to significant remote code execution risks. This weakness stems from insufficient input validation when processing document files, particularly those containing embedded macros or scripts. The flaw allows attackers to manipulate file paths in a way that bypasses normal security boundaries, enabling arbitrary code execution through maliciously crafted documents. The vulnerability specifically targets the document parsing mechanism that handles external script references, creating a pathway for attackers to access and execute code from arbitrary filesystem locations relative to the LibreOffice installation directory.
The technical implementation of this vulnerability involves the manipulation of file path references within document structures that LibreOffice uses to locate and execute embedded scripts. When a user opens a crafted document, the application processes these references without proper sanitization, allowing attackers to specify file paths that traverse parent directories using conventional path traversal sequences. This flaw falls under the CWE-22 category of "Improper Limitation of a Pathname to a Restricted Directory" and aligns with ATT&CK technique T1059.006 for "Command and Scripting Interpreter: Python" as it enables execution of Python scripts through the LibreOffice macro system. The vulnerability operates at the application layer, specifically within the document processing and script execution components, making it particularly dangerous as it can be exploited through social engineering attacks where users open seemingly legitimate documents.
The operational impact of CVE-2018-16858 extends far beyond simple document corruption or data loss, as it provides attackers with persistent access to target systems through the execution of arbitrary Python code. This capability enables attackers to perform reconnaissance, establish persistence mechanisms, and potentially escalate privileges within the victim environment. The vulnerability is particularly concerning because it requires no user interaction beyond opening the malicious document, making it susceptible to automated exploitation campaigns. Attackers can leverage this flaw to execute malicious payloads such as reverse shells, data exfiltration tools, or additional malware, while the Python execution environment provides access to system resources and libraries that could be exploited further. The attack surface includes any system running vulnerable versions of LibreOffice, particularly in enterprise environments where document sharing is common, making it a prime target for advanced persistent threat actors.
Mitigation strategies for CVE-2018-16858 focus primarily on immediate version updates to LibreOffice 6.0.7 or 6.1.3, which contain the necessary patches to prevent directory traversal attacks. Organizations should implement comprehensive patch management procedures to ensure all instances of LibreOffice are updated promptly, particularly in environments where users regularly handle external documents. Additional defensive measures include implementing application whitelisting policies that restrict execution of untrusted documents, configuring sandboxing mechanisms to isolate document processing, and deploying network-based intrusion detection systems to monitor for exploitation attempts. Security teams should also consider disabling macro execution by default in LibreOffice configurations and implementing strict file access controls that limit the application's ability to traverse filesystem directories. The vulnerability's exploitation requires user interaction through document opening, making user education about suspicious document attachments and implementing email filtering solutions crucial components of a comprehensive defense strategy. Organizations should also conduct regular vulnerability assessments to identify and remediate similar issues in other office productivity applications and document processing systems within their infrastructure.