CVE-2026-55025 in Office
Summary
by MITRE • 07/14/2026
Access of resource using incompatible type ('type confusion') in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 07/14/2026
Type confusion vulnerabilities represent a critical class of software defects that occur when a program uses a variable or object with an unexpected data type, leading to unpredictable behavior and potential exploitation. This particular vulnerability exists within Microsoft Office Excel and stems from improper handling of resource access where the application fails to validate data types during processing operations. The flaw manifests when Excel encounters certain file structures or data inputs that trigger incorrect type assumptions in memory management, creating opportunities for attackers to manipulate program execution flow through carefully crafted malicious content.
The technical implementation of this vulnerability typically involves manipulating spreadsheet files containing specially constructed data sequences that cause Excel's internal parsers to misinterpret object types during processing. When the application attempts to access resources using incompatible data types, it can lead to memory corruption scenarios where attacker-controlled data is interpreted as executable code. This type confusion often occurs in scenarios involving complex object hierarchies, dynamic data structures, or when handling external data sources where proper type validation mechanisms are insufficient or absent. The vulnerability may be triggered through various vectors including malicious Excel files opened directly, embedded objects within other Office documents, or through macro-enabled content that executes upon file access.
The operational impact of this vulnerability extends beyond simple code execution capabilities to encompass potential system compromise and data exfiltration scenarios. An attacker who successfully exploits this type confusion flaw can execute arbitrary code with the privileges of the targeted user, potentially leading to full system control when combined with other exploitation techniques. The local execution requirement means that successful exploitation typically requires user interaction such as opening a malicious file or visiting a compromised website that delivers the exploit payload through Office applications. This vulnerability aligns with ATT&CK technique T1059.005 for command and script interpreter usage, as well as T1203 for exploitation for client execution, demonstrating how type confusion can serve as a foundational attack vector in broader exploitation campaigns.
Mitigation strategies for this type confusion vulnerability should encompass both defensive programming practices and operational security measures. Organizations should implement comprehensive patch management programs ensuring timely deployment of Microsoft security updates that address known type confusion vulnerabilities within Office applications. Application whitelisting solutions and strict file extension controls can help prevent execution of potentially malicious Office documents from untrusted sources. Additionally, enabling Office's built-in security features such as Protected View mode, macro security settings, and automatic updates should be configured to minimize attack surface opportunities. Security researchers should monitor for related vulnerabilities through CWE entries describing type confusion patterns and maintain awareness of evolving exploitation techniques targeting similar memory corruption flaws within Microsoft Office products. Organizations implementing zero-trust security models should consider additional network segmentation controls and endpoint detection and response solutions that can identify anomalous Office application behavior indicative of attempted exploitation attempts.