CVE-2026-97763 in Excel
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 heap-based buffer overflow within the Microsoft Office Excel application, specifically affecting its ability to process external data inputs received over a network connection. This type of flaw arises when the software fails to properly validate the size or length of user-supplied input before copying it into a pre-allocated memory region on the heap. In this specific context, an attacker can craft a malicious file or exploit a remote code execution vector that triggers Excel to allocate insufficient buffer space for incoming data structures. When the application attempts to write the oversized payload into this limited memory block, the excess data overflows beyond the boundaries of the allocated heap segment. This overflow corrupts adjacent memory locations, potentially overwriting critical control data such as function pointers or exception handlers stored on the heap.
The operational impact of this vulnerability is severe because it allows an unauthorized attacker to achieve arbitrary code execution with the privileges of the currently logged-in user. By carefully crafting the payload within the buffer overflow, a remote adversary can manipulate the program flow to execute malicious shellcode. This capability effectively grants full control over the affected system, enabling the installation of malware, theft of sensitive data, or use of the compromised machine as part of a botnet. Since the vulnerability is triggered via network interactions, it significantly lowers the barrier for exploitation compared to local-only vulnerabilities. Attackers can potentially exploit this flaw through phishing campaigns where victims are tricked into opening malicious Excel files hosted on remote servers, thereby facilitating widespread compromise without requiring physical access or prior authentication beyond initial file interaction.
From a technical classification perspective, this issue aligns with CWE-122, which denotes heap-based buffer overflow, and is frequently associated with CWE-787 in broader contexts of out-of-bounds writes that lead to memory corruption. In terms of offensive security frameworks such as MITRE ATT&CK, this vulnerability facilitates techniques related to Initial Access via Spearphishing Attachment or Drive-by Compromise if the exploit chain involves web-based delivery mechanisms. The exploitation path typically falls under Command and Control for establishing persistence after initial compromise, leveraging the high-impact nature of remote code execution in enterprise environments where Excel is a ubiquitous tool.
Mitigation strategies must focus on both immediate remediation and long-term defensive posture improvements. Organizations should immediately apply the latest security patches released by Microsoft to address this specific heap overflow flaw within Office applications. It is crucial to ensure that automatic updates are enabled for all endpoints running vulnerable versions of Microsoft Office. Additionally, implementing application control policies such as AppLocker or Windows Defender Application Control can restrict the execution of untrusted scripts and binaries, thereby limiting the impact even if an exploit succeeds in gaining initial code execution. Network segmentation should also be reviewed to minimize lateral movement opportunities once a single endpoint is compromised. User awareness training remains vital to prevent social engineering attacks that deliver malicious Excel files designed to trigger this vulnerability upon opening.