CVE-2026-88172 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 • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Excel application, specifically categorized as an out-of-bounds read error. This type of memory corruption issue arises when software attempts to access data stored at a memory location that lies outside the boundaries of the intended buffer or array structure. In the context of Excel, this typically occurs during the parsing and rendering of complex spreadsheet files containing specially crafted formulas, embedded objects, or malformed metadata structures. When an attacker constructs a malicious document designed to exploit these specific edge cases in the application's internal logic, they can trigger the erroneous memory access sequence. The primary consequence of such a flaw is not immediate code execution but rather unauthorized information disclosure. By carefully manipulating the input data and monitoring the application's response or crash behavior, an adversary may be able to read sensitive contents from adjacent memory regions that were not intended for public exposure.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-125, which defines out-of-bounds read errors as accessing memory beyond the end of a buffer. This category of weakness is particularly dangerous because it can lead to information leakage without necessarily crashing the application immediately, allowing for stealthier exploitation attempts. The operational impact centers on confidentiality rather than integrity or availability in its initial stage. An unauthorized attacker who successfully exploits this flaw could potentially disclose internal system states, cached credentials, or other sensitive data residing in the process memory space of Excel. This disclosure can serve as a precursor to more severe attacks, such as remote code execution, by providing the attacker with valuable information about the target environment's architecture and loaded modules.
The attack vector for this vulnerability is primarily network-based if the malicious file is delivered via email attachments or downloaded from untrusted websites, fitting into the MITRE ATT&CK framework under techniques related to Initial Access through spearphishing attachment or Drive-by Compromise. The attacker relies on social engineering tactics to persuade a user to open the crafted Excel document, after which the exploit code executes within the context of the vulnerable application. This highlights the importance of user awareness alongside technical controls, as the initial trigger is often human interaction with malicious content rather than direct network exploitation against an exposed service port.
Mitigation strategies for this vulnerability involve both immediate patching and long-term defensive measures. Organizations must ensure that Microsoft Office Excel is updated to the latest version containing the security fixes provided by Microsoft in their monthly cumulative updates or out-of-band patches addressing CVE identifiers associated with these memory corruption issues. Additionally, implementing application control policies such as AppLocker or Windows Defender Application Control can restrict the execution of untrusted scripts and macros within office applications. Enabling Protected View for files originating from the internet adds an extra layer of isolation by opening potentially malicious documents in a sandboxed environment where they cannot interact with the host system's resources directly. Furthermore, deploying advanced endpoint detection and response solutions that monitor for anomalous memory access patterns or unusual process behavior can help detect exploitation attempts in real-time before significant damage occurs.