CVE-2026-97751 in Excel
Summary
by MITRE • 10/14/2026
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Excel application, specifically manifesting as a heap-based buffer overflow. This type of memory corruption error occurs when a program writes data beyond the allocated boundaries of a buffer located in the heap segment of computer memory. In the context of Excel, this typically involves the processing of complex or malformed spreadsheet files that contain specially crafted objects, formulas, or embedded content. When the application attempts to parse these inputs, it fails to adequately validate the size of the incoming data against the pre-allocated memory space. Consequently, excess data overwrites adjacent memory locations on the heap, corrupting internal data structures and control flow mechanisms such as function return addresses or exception handlers. This corruption allows an attacker who has crafted a malicious document to gain arbitrary code execution capabilities within the security context of the user running the application.
The operational impact of this vulnerability is severe due to its potential for remote exploitation over a network. An unauthorized attacker can distribute the malicious Excel file through various vectors, including email attachments, shared network drives, or web-based downloads. Upon opening the crafted document, the exploit code executes automatically without requiring further interaction from the victim in many scenarios. This leads to full system compromise, where the attacker gains the same user rights as the current logged-in user. If the affected system is configured with elevated privileges, such as administrative access, the impact escalates significantly, allowing for complete control over the operating system and network infrastructure. The attacker can install programs, view, change, or delete data, or create new accounts with full user rights, effectively neutralizing standard security controls that rely on privilege separation.
From a technical classification perspective, this vulnerability aligns closely with Common Weakness Enumeration (CWE) identifiers such as CWE-120 Buffer Copy without Checking Size of Input and CWE-787 Out-of-bounds Write in the heap space. These classifications highlight the fundamental failure in input validation and memory management that permits the overflow. Furthermore, within the MITRE ATT&CK framework, this vulnerability facilitates initial access techniques like Spearphishing Attachment or Drive-by Compromise, depending on the delivery method employed by the attacker. The exploitation chain often involves leveraging native Excel features to execute shellcode, which may subsequently lead to persistence mechanisms such as registry modifications or scheduled tasks if the attacker seeks long-term control over the compromised host.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided security patches that address the underlying memory management flaws in the Excel application logic. Organizations should prioritize updating Microsoft Office suites to include all cumulative updates released after the disclosure of this flaw. In environments where immediate patching is not feasible, administrative controls can be employed to restrict users from opening files from potentially unsafe locations or disable automatic macro execution and object instantiation within spreadsheets. Additionally, deploying endpoint detection and response solutions with behavior-based monitoring can help identify anomalous process creation events that may indicate successful exploitation of this heap overflow vulnerability before significant damage occurs.