CVE-2026-88192 in Excel
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 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 the software attempts to access data stored in memory locations that lie outside the boundaries of allocated buffers or arrays. 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 a user opens such a maliciously constructed document, the application's internal processing engine misinterprets the file structure, leading it to read memory addresses that were not intended for access by the current operation. This deviation from expected program flow allows an attacker who has successfully tricked a victim into opening the crafted file to trigger this erroneous memory access sequence remotely over a network connection or through local execution of the malicious document.
From a technical perspective, out-of-bounds reads are particularly dangerous because they facilitate information disclosure without necessarily requiring immediate code execution on the target system. The primary operational impact is the unauthorized leakage of sensitive data residing in the process memory space at the time of exploitation. This disclosed information can include cryptographic keys, session tokens, passwords, or other confidential data that was previously loaded into Excel's memory for legitimate purposes. By carefully crafting the input to control what lies adjacent to the buffer being read, an attacker can systematically extract this sensitive content and transmit it back to a remote server under their control. This capability significantly elevates the severity of the vulnerability from a simple denial-of-service risk to a high-impact confidentiality breach, potentially compromising the integrity of entire organizational networks if privileged credentials or internal network topology details are exposed.
This flaw aligns closely with Common Weakness Enumeration (CWE) identifier CWE-125, which defines out-of-bounds read vulnerabilities where software reads data past the end or before the beginning of a buffer. Furthermore, in terms of tactical classification within the MITRE ATT&CK framework, this vulnerability supports techniques associated with Initial Access and Collection phases. Attackers would likely utilize Spearphishing Attachment (T1566.001) to deliver the malicious Excel file to victims. Once executed, the exploitation mechanism facilitates Data from Local System (T1005), allowing for the exfiltration of sensitive information directly from memory. The reliance on social engineering highlights that while the technical flaw is severe, its successful exploitation often depends heavily on user interaction and awareness levels within the target organization.
Mitigation strategies must address both immediate remediation and long-term defensive posture improvements. Organizations should immediately apply the latest security updates provided by Microsoft for all installations of Office Excel to patch this specific memory handling defect. Beyond software patching, implementing application control policies such as AppLocker or Windows Defender Application Control can prevent unauthorized scripts from running within Office applications, thereby reducing the attack surface even if a vulnerability is present. Additionally, deploying advanced email filtering solutions that inspect attachments for malicious patterns and sandbox suspicious files before delivery to end-users can significantly reduce the likelihood of successful exploitation. User training programs focused on recognizing phishing attempts and verifying the source of unexpected documents remain critical layers of defense against this type of social engineering-driven attack vector.