CVE-2026-55134 in Word
Summary
by MITRE • 07/14/2026
Stack-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 07/15/2026
A stack-based buffer overflow vulnerability exists in Microsoft Office Word that enables unauthorized attackers to execute arbitrary code on a target system with local privileges. This critical security flaw stems from improper input validation within the word processing application's memory management routines, specifically when handling malformed or oversized data inputs in document parsing operations. The vulnerability manifests when the application attempts to write data beyond the bounds of a pre-allocated stack buffer, creating conditions that allow attackers to overwrite adjacent memory locations including return addresses and control flow information.
The technical implementation of this vulnerability involves the exploitation of memory corruption patterns that occur during document processing operations such as text rendering, formatting, or embedded object handling. When an attacker crafts a specially malformed word document containing oversized data structures or malicious payload sequences, the application's insufficient bounds checking allows the overflow to occur. This memory corruption can be leveraged to redirect program execution to attacker-controlled code locations within the process memory space. The flaw operates at the application layer with no network requirements for exploitation, making it particularly dangerous as it only requires local execution privileges and user interaction through document opening.
The operational impact of this vulnerability extends beyond simple code execution, potentially enabling full system compromise when combined with privilege escalation techniques or when users open malicious documents from untrusted sources. Attackers can leverage this vulnerability to install backdoors, steal sensitive data, modify system configurations, or establish persistent access points within the compromised environment. The attack surface is significantly broadened as Microsoft Word remains one of the most widely used applications across enterprise and consumer environments, increasing the potential for widespread exploitation.
Security mitigations for this vulnerability should encompass multiple defensive layers including immediate patch deployment from Microsoft security updates, application whitelisting policies to restrict execution of unauthorized code, and user education regarding document safety practices. Network segmentation and endpoint protection solutions can provide additional defense-in-depth measures while monitoring for suspicious execution patterns or memory manipulation activities. Organizations should implement mandatory security updates across all systems running affected Office versions and consider disabling unnecessary Word features such as macro execution or automatic document loading from untrusted sources. This vulnerability aligns with CWE-121 stack-based buffer overflow classification and can be mapped to ATT&CK technique T1059 for command and scripting interpreter usage, while also representing a common pathway for privilege escalation attacks through local code execution.