CVE-2026-55122 in Office
Summary
by MITRE • 07/14/2026
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 07/15/2026
This vulnerability represents a critical out-of-bounds read flaw within Microsoft Office Excel that enables local attackers to extract sensitive information from memory locations beyond the intended buffer boundaries. The technical implementation involves improper input validation and boundary checking mechanisms within Excel's spreadsheet processing engine, specifically when handling malformed or specially crafted Excel files. Such vulnerabilities typically arise from insufficient bounds checking during array or buffer operations, allowing attackers to read data from adjacent memory regions that may contain confidential information including but not limited to user credentials, system paths, encryption keys, or other sensitive operational data.
The operational impact of this vulnerability extends beyond simple information disclosure as it creates potential pathways for further exploitation. Attackers can leverage this primitive to gather intelligence about the target system's memory layout, which serves as foundational knowledge for more sophisticated attacks including privilege escalation or remote code execution attempts. The local nature of this vulnerability means that attackers must already have access to the target system through other means such as phishing, social engineering, or previous compromise techniques, but once achieved, they can utilize this information disclosure to enhance their foothold within the environment.
From a cybersecurity framework perspective, this vulnerability maps directly to CWE-129 Input Validation and Bounds Checking and aligns with ATT&CK technique T1059 Command and Scripting Interpreter where attackers might use information disclosed through such vulnerabilities to craft more effective attack vectors. The flaw essentially represents a memory safety issue that could be exploited as part of a broader attack chain, particularly when combined with other vulnerabilities or when the attacker has already established initial access through different means. Organizations should prioritize immediate patch management for this vulnerability while implementing additional defensive measures including application whitelisting, user education programs, and network monitoring to detect potential exploitation attempts.
The root cause analysis reveals that Excel's parsing logic fails to properly validate array indices or buffer boundaries during spreadsheet processing operations, particularly when encountering malformed data structures within Excel files. This type of vulnerability often stems from legacy code implementations where memory management practices did not adequately account for modern security requirements, making it particularly dangerous in enterprise environments where Excel is widely used for business operations and data processing. Security teams should consider this vulnerability as part of their comprehensive threat modeling exercises, especially when evaluating risks associated with file-based attacks and the potential for information leakage within document processing applications.
Effective mitigation strategies include immediate deployment of Microsoft security updates and patches, implementation of strict file validation policies, and enhanced monitoring of suspicious Excel file operations within network environments. Organizations should also consider implementing sandboxing technologies for Excel processing, restricting user permissions when handling external spreadsheet files, and conducting regular security assessments to identify similar vulnerabilities within other office productivity applications that may share common code bases or processing mechanisms with Excel.