CVE-2026-97756 in Office
Summary
by MITRE • 10/15/2026
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 • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Excel application, specifically manifesting as a heap-based buffer overflow condition. 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 parsing logic errors within the application's rendering engine. The root cause lies in insufficient validation checks performed by the software when handling input data, allowing an attacker to supply a payload that exceeds the expected buffer size and overwrites adjacent memory structures on the heap.
The operational impact of this vulnerability is severe due to its potential for remote code execution without user interaction beyond opening or viewing the malicious file. An unauthorized attacker can leverage this flaw by hosting a specially crafted Excel document on a web server or distributing it via email attachments. When a victim opens the compromised file, the malformed data triggers the buffer overflow during the application's parsing process. This memory corruption allows the injection and execution of arbitrary code within the security context of the current user. Consequently, an attacker could gain full control over the affected system, install programs, view, change, or delete data, or create new accounts with full user rights. If the current user is logged on with administrative privileges, the impact is even more catastrophic as it grants complete control over all resources on the machine.
From a classification perspective, this vulnerability aligns closely with Common Weakness Enumeration identifier CWE-120, which describes Buffer Copy without Checking Size of Input Classic Heap Overflow. The exploitation technique often involves manipulating data structures such as linked lists or object headers within the heap to achieve arbitrary write primitives, which are then chained together to facilitate code execution. In terms of adversary tactics and techniques, this scenario maps directly to MITRE ATT&CK Technique T1203, specifically sub-technique T1203.2 Exploitation for Client Execution. This technique highlights how attackers exploit vulnerabilities in software applications used by clients rather than servers, relying on social engineering or drive-by download mechanisms to trigger the initial execution vector through legitimate-looking documents like spreadsheets.
Mitigation strategies must focus on both immediate remediation and long-term defense-in-depth measures. The primary corrective action is to apply the latest security updates provided by Microsoft for all versions of Office Excel affected by this vulnerability. Organizations should enforce automated patch management policies to ensure timely deployment of these fixes across all endpoints. Additionally, implementing application control solutions such as AppLocker or Windows Defender Application Control can restrict the execution of untrusted scripts and binaries from temporary folders where downloaded files are often stored. Network segmentation and strict firewall rules limiting outbound connections from workstations can also reduce the blast radius in case of a successful compromise. Users should be educated to exercise caution when opening attachments from unknown sources and to disable automatic macro execution, as many exploits rely on enabling macros to achieve persistence or further lateral movement after initial code execution.