CVE-2026-68816 – Microsoft Excel Remote Code Execution Vulnerability

CVE-2026-68816 is a Critical remote code execution vulnerability caused by a stack-based buffer overflow in Microsoft Office Excel. An attacker can send a specially crafted Office file and convince a user to open it, triggering the vulnerability locally. Successful exploitation can result in high impact to confidentiality, integrity, and availability.

CVSS Score: 7.8.

SEVERITY: Critical.

THREAT:
An attacker can use a malicious Office file to trigger a stack-based buffer overflow and execute code on the affected system. Attack complexity is low and no privileges are required, although user interaction is required. The Preview Pane is not an attack vector.

EXPLOITS:
The vulnerability is not publicly disclosed and is not known to be exploited. Exploit code maturity is Unproven, and exploitation is assessed as Less Likely. No confirmed public exploit, zero-day exploitation, or proof-of-concept exploit code is identified.

TECHNICAL SUMMARY:
CVE-2026-68816 is a stack-based buffer overflow vulnerability (CWE-121) affecting Microsoft Office Excel. Exploitation requires an attacker to deliver a malicious Office file and persuade the victim to open it. Although classified as remote code execution because the attacker may be remote, the malicious code is executed locally on the victim's machine. The attack has low complexity, requires no privileges, and requires user interaction. Successful exploitation can execute unauthorized code and cause high confidentiality, integrity, and availability impact.

EXPLOITABILITY:
Affected products include Microsoft 365 Apps for Enterprise (32-bit and 64-bit), Excel 2016 (32-bit and 64-bit), Office 2019 (32-bit and 64-bit), Office 365 for Mac, Office LTSC 2021 and 2024 (32-bit and 64-bit), and Office LTSC for Mac 2021 and 2024. Exploitation requires a user to open a malicious Office file.

BUSINESS IMPACT:
Successful exploitation could allow unauthorized code execution on employee systems, potentially exposing sensitive information, modifying data, or disrupting system availability. A convincing malicious document could turn ordinary document handling into a significant security incident.

WORKAROUND:
No workaround or mitigation is identified. An official fix is identified as the remediation.

URGENCY:
This vulnerability carries a Critical severity rating and can result in remote code execution with high confidentiality, integrity, and availability impact. Organizations should prioritize deployment of the official fix across affected Microsoft Office and Excel installations, particularly systems where users regularly receive Office documents from external sources.