CVE-2026-97762 in Excel
Summary
by MITRE • 10/15/2026
Out-of-bounds write 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 involves a critical out-of-bounds write flaw within the Microsoft Office Excel application, specifically affecting its ability to process certain document structures or data inputs. This type of memory corruption error occurs when the software writes data beyond the boundaries of an allocated buffer in system memory. In the context of network-based attacks, this typically implies that a malicious actor can craft a specially designed file or exploit a specific feature within Excel that is triggered during remote access scenarios, such as opening a document from a shared drive, downloading it via email attachments, or accessing content through SharePoint services. The core technical flaw lies in insufficient validation checks performed by the application before writing data to memory locations, allowing an attacker to overwrite adjacent memory structures with arbitrary values.
From a security architecture perspective, this vulnerability aligns closely with CWE-787, which defines out-of-bounds write as accessing memory outside of intended boundaries. The operational impact is severe because successful exploitation can lead to remote code execution (RCE), granting the unauthorized attacker full control over the affected system under the context of the current user. This capability allows for further lateral movement within a corporate network, data exfiltration, or installation of persistent backdoors. The attack vector falls squarely into MITRE ATT&CK technique T1203, which covers exploitation for client execution, where adversaries leverage vulnerabilities in software applications to execute malicious code on target systems without direct user interaction beyond opening the file.
The severity of this issue is amplified by its network-based nature and the ubiquity of Microsoft Office products across enterprise environments. Attackers often combine such memory corruption flaws with other techniques like heap spraying or return-oriented programming (ROP) chains to bypass modern mitigations such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR). By carefully crafting the payload, an attacker can redirect execution flow to malicious shellcode embedded within the malformed Excel file. This results in a complete compromise of confidentiality, integrity, and availability for any user who opens the crafted document, particularly if they lack sufficient administrative privileges or sandboxing protections.
To mitigate this risk, organizations must prioritize immediate patching by applying the latest security updates released by Microsoft to all endpoints running vulnerable versions of Excel. Beyond software remediation, implementing application control policies such as Windows Defender Application Control (WDAC) can restrict the execution of untrusted scripts and binaries. Additionally, enabling Protected View for files originating from the internet or unsafe locations adds a layer of isolation that prevents automatic code execution upon opening suspicious documents. Network segmentation should also be enforced to limit lateral movement in case an endpoint is compromised, ensuring that even if exploitation occurs, the attacker's ability to propagate across the network remains constrained. Regular security awareness training for employees regarding phishing and malicious file handling further reduces the likelihood of successful initial access through social engineering tactics targeting this specific vulnerability class.