CVE-2026-55037 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 flaw resides in the application's handling of specific data structures within the spreadsheet processing engine, where insufficient bounds checking allows an attacker to overwrite adjacent memory locations on the heap. The vulnerability specifically manifests when Excel processes certain malformed or specially constructed worksheet elements that trigger improper memory allocation and data copying operations.
The technical implementation of this vulnerability involves the exploitation of memory management functions within Excel's parsing routines for various file formats including xls, xlsx, and xlsm. Attackers can craft malicious spreadsheet files that contain oversized data structures or malformed records which cause the application to allocate insufficient heap space for incoming data. When subsequent processing operations attempt to write beyond these allocated boundaries, adjacent memory regions become overwritten with attacker-controlled data, potentially corrupting function pointers, return addresses, or other critical execution metadata.
From an operational perspective this vulnerability represents a significant threat vector in enterprise environments where Excel remains one of the most commonly used applications for data processing and collaboration. The attack requires minimal user interaction beyond opening the malicious file, making it particularly dangerous in phishing campaigns or targeted attacks against specific individuals within organizations. The exploitation typically results in arbitrary code execution with the privileges of the compromised user account, potentially leading to full system compromise if the user has administrative rights.
The vulnerability aligns with common weakness enumeration CWE-121 heap-based buffer overflow and maps to multiple techniques within the attack chain framework including initial access through malicious file delivery and privilege escalation via code execution. Organizations should implement immediate mitigations such as applying Microsoft's security patches, enabling macro security controls, and deploying application whitelisting solutions that restrict execution of untrusted Office documents. Network-level protections including email filtering and web proxy configurations can help prevent delivery of malicious files, while endpoint detection and response systems should monitor for suspicious memory allocation patterns or process behavior indicative of exploitation attempts.
This vulnerability demonstrates the ongoing challenges in securing complex office productivity applications where extensive feature sets create numerous potential attack surfaces. The heap-based nature of the flaw makes it particularly difficult to detect through traditional signature-based approaches, requiring more sophisticated behavioral analysis and exploit prevention mechanisms. Security teams should prioritize patch management for Office applications while maintaining awareness of similar vulnerabilities in other Microsoft Office products that may present analogous exploitation vectors through shared codebases and processing engines.