CVE-2026-55129 in Office
Summary
by MITRE • 07/14/2026
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 07/15/2026
A heap-based buffer overflow vulnerability exists within Microsoft Office applications that enables remote code execution by malicious actors who gain local access to a target system. This critical security flaw arises from improper memory management during the processing of specially crafted Office documents, specifically when handling certain data structures in memory. The vulnerability manifests when the application attempts to write more data into a heap-allocated buffer than it can accommodate, causing adjacent memory locations to be overwritten with attacker-controlled data.
The technical implementation of this vulnerability involves the exploitation of memory corruption patterns that occur during document parsing operations within Microsoft Office suites. When an Office application processes maliciously formatted files such as word documents, excel spreadsheets, or powerpoint presentations, it allocates memory on the heap for various data elements including strings, arrays, and complex objects. The buffer overflow occurs when input validation fails to properly constrain the size of data being written into these heap-allocated memory regions, allowing attackers to overwrite critical memory pointers, return addresses, or function metadata that controls program execution flow.
From an operational perspective, this vulnerability presents a severe risk to enterprise environments where Microsoft Office applications are widely deployed across organizational networks. Attackers can leverage this flaw by delivering malicious Office documents through various attack vectors including email attachments, web downloads, or removable media, requiring only local access to execute code on target systems. The exploitation process typically involves crafting specific document structures that trigger the buffer overflow condition when opened by vulnerable Office applications, potentially leading to full system compromise and persistence mechanisms. This vulnerability aligns with CWE-121 heap-based buffer overflow classification and represents a significant concern for security teams managing Microsoft Office deployments.
The impact of this vulnerability extends beyond individual system compromise to encompass broader enterprise risks including data exfiltration, lateral movement within networks, and establishment of persistent backdoors. Organizations utilizing Microsoft Office applications face potential disruption from targeted attacks that exploit this weakness, particularly in environments where users frequently open external documents without proper security controls. The remediation approach requires immediate application of Microsoft security patches and updates to address the underlying memory management issues within Office applications. Security professionals should implement network monitoring for suspicious document handling activities and consider deploying application whitelisting solutions to restrict execution of potentially malicious Office files.
This vulnerability demonstrates the persistent challenges associated with memory safety in complex software applications and highlights the importance of robust input validation and memory management practices. The exploitation techniques commonly employed by threat actors leverage modern exploit development methodologies including return-oriented programming and heap spraying to achieve reliable code execution on vulnerable systems. Organizations should maintain comprehensive patch management programs and consider implementing additional security controls such as sandboxing mechanisms for document processing, email filtering solutions, and user education initiatives to reduce the attack surface associated with Office-based vulnerabilities. The underlying principles of this vulnerability also relate to ATT&CK technique T1059.005 which covers command and scripting interpreter usage in malicious contexts.
Microsoft has addressed this vulnerability through security updates that improve memory allocation handling and input validation within Office applications, requiring organizations to deploy these patches promptly to mitigate the risk of exploitation. Security teams should conduct thorough vulnerability assessments to identify systems running affected versions of Microsoft Office and prioritize patch deployment based on risk assessment criteria. The continued existence of such vulnerabilities underscores the critical need for ongoing security research and proactive remediation strategies in enterprise environments where office productivity applications remain essential components of daily operations.