CVE-2026-55036 in Office
Summary
by MITRE • 07/14/2026
Buffer over-read in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 07/15/2026
This vulnerability represents a critical buffer over-read condition within Microsoft Office Excel that enables remote code execution under specific circumstances. The flaw occurs when the application processes malformed spreadsheet files, particularly those containing crafted data structures that exceed allocated memory boundaries during parsing operations. Such buffer over-reads typically arise from insufficient input validation and boundary checking mechanisms within the spreadsheet engine's memory management subsystem. The vulnerability falls under the CWE-125 category of out-of-bounds read conditions, which directly relates to improper handling of memory access operations.
The technical exploitation of this vulnerability requires an attacker to craft a malicious excel file that triggers the buffer over-read during normal document processing. When Excel attempts to parse the malformed data structure, it reads beyond the allocated memory buffer, potentially accessing adjacent memory locations containing executable code or control data. This memory corruption can lead to arbitrary code execution within the context of the user running the vulnerable application. The attack vector typically involves social engineering techniques where users unknowingly open malicious spreadsheet files through email attachments, web downloads, or removable media.
From an operational impact perspective, this vulnerability poses significant risks to enterprise environments where Microsoft Office is widely deployed across organizational networks. The local code execution capability allows attackers to establish persistent access, escalate privileges, and potentially move laterally within the network. The vulnerability affects multiple versions of Excel across different operating systems including windows desktop and server environments. Organizations with default user configurations that automatically open attachments or have less restrictive security policies face heightened exposure risk.
Security mitigations for this vulnerability should include immediate deployment of Microsoft security patches and updates to address the underlying buffer over-read condition. Network administrators should implement email filtering solutions that scan for suspicious file attachments and employ application whitelisting policies to restrict execution of unauthorized excel files. Users must be trained to recognize phishing attempts and avoid opening unexpected spreadsheet files from untrusted sources. Additionally, organizations should configure Excel's security settings to disable automatic execution of macros and enable protected view mode for files from unknown origins. The ATT&CK framework categorizes this vulnerability under initial access and execution techniques where adversaries leverage application vulnerabilities to establish footholds within target environments.
The vulnerability demonstrates how seemingly benign office productivity applications can become attack vectors when memory safety mechanisms fail to properly validate input data. This particular flaw highlights the importance of robust memory management practices in commercial software development and the critical need for comprehensive security testing of widely deployed applications. Organizations must maintain vigilant patch management processes and implement defense-in-depth strategies to protect against such exploitation methods that leverage application-level vulnerabilities for unauthorized code execution.