CVE-2026-55041 in Office
Summary
by MITRE • 07/14/2026
Heap-based buffer overflow in Microsoft Office Excel 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 in Microsoft Office Excel that enables remote code execution when a maliciously crafted file is opened by an unsuspecting user. This vulnerability stems from insufficient input validation within the application's handling of malformed spreadsheet data structures, specifically affecting how Excel processes certain workbook elements during parsing operations. The flaw occurs when Excel attempts to allocate memory on the heap for processing corrupted or oversized data segments, leading to memory corruption that can be exploited by attackers to overwrite adjacent memory locations with malicious code.
The technical implementation of this vulnerability involves the exploitation of memory management functions within Excel's core processing engine where heap allocations are performed without adequate bounds checking. When a user opens a specially crafted excel file containing oversized or malformed data structures, the application fails to properly validate the size parameters before allocating memory buffers on the heap. This allows an attacker to control the amount of memory allocated and subsequently overwrite adjacent heap memory regions with carefully crafted malicious payload data. The vulnerability is particularly dangerous because it can be triggered through standard user interactions without requiring any specialized privileges or additional attack vectors.
From an operational impact perspective, this vulnerability poses significant risks to enterprise environments where Excel files are commonly shared via email attachments, file sharing systems, and collaborative platforms. Attackers can craft malicious excel files that appear legitimate to end users, making social engineering attacks highly effective in compromising target systems. Once successfully exploited, the remote code execution capability allows attackers to establish persistent access, escalate privileges, and potentially move laterally within network environments. The vulnerability affects multiple versions of Microsoft Office and Windows operating systems, creating widespread exposure across enterprise networks.
Organizations should implement immediate mitigations including deploying Microsoft security patches and updates as soon as they become available, configuring application whitelisting policies to restrict execution of untrusted excel files, and implementing email filtering solutions that can detect and quarantine potentially malicious attachments. Network segmentation and monitoring solutions should be enhanced to detect unusual file access patterns and potential exploitation attempts. Security teams must also conduct regular vulnerability assessments targeting office productivity applications and ensure proper user education regarding the risks of opening unknown or unexpected excel files. This vulnerability aligns with CWE-121 heap-based buffer overflow classifications and represents a common attack pattern documented in MITRE ATT&CK framework under technique T1059 for execution through command and scripting interpreters, highlighting the importance of comprehensive endpoint protection strategies.