CVE-2017-7870 in LibreOffice
Summary
by MITRE
LibreOffice before 2017-01-02 has an out-of-bounds write caused by a heap-based buffer overflow related to the tools::Polygon::Insert function in tools/source/generic/poly.cxx.
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Analysis
by VulDB Data Team • 11/29/2022
The vulnerability identified as CVE-2017-7870 represents a critical heap-based buffer overflow affecting LibreOffice versions prior to the 2017-01-02 release. This flaw manifests within the tools::Polygon::Insert function located in tools/source/generic/poly.cxx, demonstrating a classic out-of-bounds write condition that can lead to arbitrary code execution. The vulnerability stems from insufficient input validation and boundary checking when processing polygonal data structures, creating an exploitable condition where attacker-controlled data can overwrite adjacent memory regions. The heap-based nature of this overflow indicates that the vulnerable code operates on dynamically allocated memory segments, making the exploitation vector particularly dangerous as it can corrupt heap metadata and potentially lead to remote code execution.
The technical implementation of this vulnerability involves the manipulation of polygon data structures within LibreOffice's generic tools library, where the Insert function fails to properly validate array indices or buffer boundaries when adding new points to polygon objects. This flaw aligns with CWE-121, which categorizes heap-based buffer overflow conditions, and specifically maps to the broader category of CWE-787, representing out-of-bounds write vulnerabilities. The vulnerability can be triggered through malformed document files or specially crafted polygon data that causes the application to attempt writing beyond the allocated memory buffer. Attackers can exploit this condition by preparing malicious documents that, when opened by an affected LibreOffice version, will cause the application to crash or execute arbitrary code with the privileges of the user running the application.
The operational impact of CVE-2017-7870 extends beyond simple application instability, as it represents a significant security risk in enterprise environments where LibreOffice is widely deployed for document processing. The vulnerability can be exploited through social engineering attacks where users open malicious documents, potentially leading to complete system compromise. Given that LibreOffice is commonly used in business and government settings for creating and editing documents, the attack surface is extensive. This vulnerability also aligns with ATT&CK technique T1203, which covers exploitation of software vulnerabilities, and T1059, representing command and scripting interpreter usage, as successful exploitation could enable attackers to execute additional payloads or establish persistence within affected systems. Organizations utilizing older versions of LibreOffice face heightened risk of targeted attacks, particularly in environments where document exchange occurs frequently with external parties.
Mitigation strategies for CVE-2017-7870 primarily focus on immediate remediation through patching, as the vulnerability has been addressed in LibreOffice version 5.3.2 and subsequent releases. System administrators should prioritize updating all LibreOffice installations to versions containing the fix, which implements proper bounds checking and input validation for the polygon insertion function. Additional protective measures include implementing application whitelisting policies to restrict execution of untrusted documents, deploying sandboxing solutions to isolate LibreOffice processes, and configuring network-based intrusion detection systems to monitor for exploitation attempts. The vulnerability also underscores the importance of regular security assessments and maintaining up-to-date software inventory to identify and remediate similar issues across the enterprise. Organizations should also consider implementing automated patch management solutions to ensure timely deployment of security updates and reduce the window of exposure for known vulnerabilities.