CVE-2026-88190 in 365 Apps for Enterprise
Summary
by MITRE • 10/14/2026
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified as an out-of-bounds read within Microsoft Office Excel represents a critical memory safety flaw that compromises the confidentiality of system data through remote exploitation vectors. This specific type of error occurs when the application attempts to access memory locations beyond the boundaries of allocated buffers, typically due to insufficient validation of input parameters or improper handling of malformed file structures. In the context of spreadsheet applications like Excel, this often involves parsing complex formulas, embedded objects, or specially crafted data sets that trigger incorrect pointer arithmetic during rendering or calculation processes. When such a condition is met, the application reads arbitrary memory contents rather than throwing an exception or halting execution, thereby exposing sensitive information stored in adjacent memory regions to potential attackers.
From a technical perspective, this flaw aligns with Common Weakness Enumeration category CWE-125, which describes out-of-bounds read vulnerabilities where software reads data past the end of a buffer. The operational impact is primarily focused on unauthorized information disclosure rather than immediate code execution or privilege escalation, although in some scenarios, such leaks can serve as precursors to more severe attacks like heap spraying for arbitrary code execution. An attacker who successfully exploits this vulnerability could potentially extract credentials, session tokens, cryptographic keys, or other sensitive data residing in the process memory space of Excel. This disclosure occurs over a network if the victim is tricked into opening a maliciously crafted document hosted on a remote server or received via email attachment, making it a significant threat for organizations relying on collaborative file sharing and external communications.
The exploitation mechanism typically relies on social engineering tactics to deliver the payload, as direct network access alone does not trigger the vulnerability without user interaction such as clicking a link or opening an attached file. This behavior is consistent with ATT&CK technique T1204, User Execution, where adversaries use malicious content to execute code by tricking users into performing actions that bypass security measures. The presence of this flaw indicates gaps in input validation logic within the Excel parsing engine, particularly regarding how it handles edge cases in data types and memory allocation strategies for dynamic arrays or complex object references.
Mitigation efforts must prioritize both technical controls and user awareness training. Organizations should ensure that Microsoft Office applications are updated with the latest security patches released by vendor to address these specific memory corruption issues. Additionally, implementing application whitelisting policies can restrict the execution of untrusted scripts or macros often associated with exploit delivery mechanisms. Network segmentation and strict email filtering rules further reduce the attack surface by preventing malicious documents from reaching end-user devices in the first place. Regular vulnerability assessments focused on office suite configurations help identify systems running outdated versions that lack these critical memory safety fixes, ensuring a robust defense against information disclosure threats stemming from out-of-bounds read conditions.