CVE-2026-55031 in Office
Summary
by MITRE • 07/14/2026
Out-of-bounds 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 memory corruption flaw that exists within Microsoft Office Excel's handling of malformed spreadsheet files, specifically affecting the application's ability to process certain data structures without proper bounds checking. The out-of-bounds read occurs when Excel attempts to access memory locations beyond the allocated buffer boundaries while parsing maliciously crafted excel files, creating a potential code execution vector that can be exploited by remote attackers. Such vulnerabilities typically arise from insufficient input validation and improper memory management within the application's parsing routines, where the software fails to verify array indices or data structure dimensions before accessing memory regions. The flaw manifests when Excel encounters specially constructed data within spreadsheet files that triggers an unexpected memory access pattern, potentially allowing an attacker to read sensitive data from memory or manipulate execution flow to achieve arbitrary code execution on the target system. This type of vulnerability is categorized under common weakness enumeration cw 129 which specifically addresses issues related to insufficient boundary checking in software applications, making it a prime target for exploitation by threat actors seeking to gain unauthorized access to systems through social engineering or drive-by download attacks.
The operational impact of this vulnerability extends beyond simple privilege escalation as it can enable full system compromise when users open maliciously crafted excel files through normal office operations. Attackers can leverage this flaw by embedding specially constructed data within excel documents that, when opened by vulnerable versions of Excel, trigger the out-of-bounds read condition. The exploitation process typically involves crafting a malicious spreadsheet file that contains malformed data structures designed to cause the memory corruption during parsing. Once successfully exploited, the vulnerability allows attackers to execute arbitrary code with the privileges of the user running the affected application, potentially leading to complete system compromise, data exfiltration, or deployment of additional malware payloads. This vulnerability aligns with attack technique t1203 in the mitre att&ck framework which covers exploitation for client execution through malicious file attachments, demonstrating how such flaws can be weaponized in targeted attacks against enterprise environments where excel files are commonly shared and opened.
Mitigation strategies for this vulnerability require immediate patching of affected Microsoft Office versions with the latest security updates provided by microsoft, as well as implementing defensive measures such as enabling macro security settings and restricting user permissions when opening office documents. Organizations should deploy email filtering solutions that can identify and block malicious excel attachments, while also establishing robust endpoint detection and response capabilities to monitor for suspicious execution patterns or memory access violations. Additional protective measures include implementing application whitelisting policies that restrict the execution of unauthorized applications, configuring excel to open files in protected view mode by default, and maintaining comprehensive backup strategies to ensure rapid recovery from potential exploitation attempts. The vulnerability highlights the importance of regular security updates and proper input validation practices within office productivity software, as well as the necessity for organizations to maintain situational awareness regarding known vulnerabilities in widely deployed applications like microsoft office through continuous monitoring of security advisories and threat intelligence feeds.