CVE-2026-97758 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.
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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 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 elements designed to exploit specific parsing routines within the application's engine. The attacker crafts input data that exceeds the expected size limits defined by the software for a particular buffer allocation, causing excess data to overwrite adjacent memory locations on the heap. This overwriting can corrupt internal pointers, function return addresses, or other critical control structures used by the Excel process during execution.
The operational impact of this vulnerability is severe due to its potential for remote code execution without user interaction beyond opening the malicious file. Because Microsoft Office applications are widely deployed across enterprise and personal environments, they represent a high-value target for threat actors. An unauthorized attacker can leverage this heap overflow to inject arbitrary shellcode into the memory space of the Excel process. By carefully controlling the overwritten data, the attacker gains the ability to execute commands with the same privileges as the currently logged-in user. This capability allows for full system compromise, including the installation of malware, theft of sensitive documents stored locally or in connected cloud services, and using the compromised machine as a pivot point for further lateral movement within a network infrastructure.
From an industry standards perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-122, which denotes heap-based buffer overflow. The exploitation technique is consistent with ATT&CK tactic T1059, specifically Command and Scripting Interpreter subtechniques, as the attacker utilizes the compromised application environment to execute arbitrary code. Furthermore, if the vulnerability allows for execution without direct user interaction beyond file opening, it may also relate to CWE-20, Improper Input Validation, indicating that the software failed to adequately sanitize or validate the size of input data before processing it into memory structures. The network aspect implies that the attack vector can be delivered via email attachments, shared drives, or web downloads, making detection and prevention challenging without robust endpoint protection mechanisms.
Mitigation strategies for this vulnerability primarily involve applying the latest security patches released by Microsoft to update Excel and related Office components. Organizations should enforce strict patch management policies to ensure all endpoints are updated promptly after vendor releases. Additionally, implementing application control solutions such as Windows Defender Application Control or AppLocker can restrict the execution of untrusted scripts and binaries, thereby limiting the impact even if an exploit succeeds. Users should be educated on social engineering tactics often used to deliver malicious Office files, including disabling macro content by default unless explicitly trusted. Network segmentation and monitoring for anomalous process creation events associated with office applications can also aid in early detection and containment of such attacks.