CVE-2026-42831 – Microsoft Office Remote Code Execution Vulnerability

A critical remote code execution vulnerability exists in Microsoft Office due to a heap-based buffer overflow. An unauthorized attacker could exploit this issue by sending a malicious Office file and convincing a user to open it. The Preview Pane is not an attack vector for this vulnerability.

CVSS Score: 7.8
SEVERITY: Critical
THREAT:
This vulnerability could allow an attacker to execute code locally on an affected system. Successful exploitation may lead to malware installation, data theft, workstation compromise, and possible movement deeper into the organization.

EXPLOITS:
At the time of publication, Microsoft reports that the vulnerability was not publicly disclosed and was not exploited. Exploit Code Maturity is listed as Unproven, and exploitation is assessed as Unlikely.

TECHNICAL SUMMARY:
CVE-2026-42831 is caused by a heap-based buffer overflow in Microsoft Office. The flaw may allow malicious Office content to corrupt memory and execute attacker-controlled code on the local machine. Although the title uses “Remote Code Execution,” the CVSS attack vector is Local, meaning exploitation requires the malicious file to be opened locally by the user. User interaction is required, and Preview Pane exploitation is not supported.

EXPLOITABILITY:
Affected Microsoft Office versions are not listed in the provided data. Exploitation requires an attacker to send a malicious Office file and convince the user to open it.

BUSINESS IMPACT:
A successful exploit could compromise employee workstations, expose sensitive documents, enable credential theft, and support phishing-based intrusion campaigns. Office file attacks are especially dangerous because they blend into normal business communication.

WORKAROUND:
No mitigations or workarounds are listed. Apply the official Microsoft fix when available for the affected Office products.

URGENCY:
This vulnerability should be prioritized because it is rated Critical and can lead to code execution through malicious Office documents. Even though exploitation is currently assessed as unlikely, Office-based attacks remain a common and effective entry point into enterprise environments.