CVE-2016-4324 in LibreOffice
Summary
by MITRE
Use-after-free vulnerability in LibreOffice before 5.1.4 allows remote attackers to execute arbitrary code via a crafted RTF file, related to stylesheet and supercript tokens.
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Analysis
by VulDB Data Team • 09/01/2022
The CVE-2016-4324 vulnerability represents a critical use-after-free flaw in LibreOffice versions prior to 5.1.4 that enables remote code execution through malicious RTF file manipulation. This vulnerability specifically targets the document processing engine's handling of RTF format files, exploiting memory management issues that occur during stylesheet and superscript token processing. The flaw arises from improper memory deallocation and subsequent reuse of memory blocks that should have been freed after stylesheet processing, creating a scenario where attackers can manipulate memory contents to execute arbitrary code on vulnerable systems.
The technical implementation of this vulnerability involves the manipulation of RTF document structures to trigger specific parsing sequences that lead to memory corruption. When LibreOffice processes a crafted RTF file containing maliciously constructed stylesheet definitions and superscript tokens, the parser fails to properly manage memory references during the processing lifecycle. This use-after-free condition occurs because the application allocates memory for stylesheet objects and then frees it, but continues to reference the freed memory location during superscript token processing. The vulnerability is particularly dangerous because RTF files are commonly encountered in email attachments and web downloads, making exploitation vectors abundant and easily accessible to remote attackers.
The operational impact of CVE-2016-4324 extends beyond simple remote code execution to encompass complete system compromise potential. Attackers can leverage this vulnerability to install malware, establish persistent backdoors, or escalate privileges within the victim's environment. The vulnerability's remote exploitability means that users need only open a malicious RTF file to be compromised, making it particularly effective for phishing campaigns and social engineering attacks. This flaw directly relates to CWE-416, which addresses use-after-free vulnerabilities, and aligns with ATT&CK technique T1059 for command and scripting interpreter usage, as successful exploitation typically leads to arbitrary code execution capabilities. The vulnerability affects multiple operating systems including Windows, Linux, and macOS where LibreOffice is installed, creating widespread exposure across enterprise and personal computing environments.
Mitigation strategies for CVE-2016-4324 primarily focus on immediate patch deployment and operational security measures. Organizations should prioritize updating to LibreOffice version 5.1.4 or later, which contains the necessary memory management fixes and defensive programming improvements. Network administrators should implement email filtering and web content restrictions to prevent delivery of potentially malicious RTF files, while security teams should monitor for indicators of compromise related to this vulnerability. The fix implemented by LibreOffice developers addresses the core memory management issue by ensuring proper reference counting and memory deallocation during stylesheet processing, preventing the reuse of freed memory blocks. Additionally, users should be educated about the risks of opening RTF files from untrusted sources and should maintain updated antivirus signatures that can detect known malicious RTF file patterns. The vulnerability demonstrates the importance of proper memory management in document processing applications and highlights the need for regular security updates in office productivity suites.