CVE-2026-42831 Microsoft Office Remote Code Execution Vulnerability
An unauthorized attacker can execute code locally via a heap-based buffer overflow in Microsoft Office, requiring users to apply vendor patches.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-42831?
CVE-2026-42831 is a high-severity memory corruption vulnerability in Microsoft 365 Copilot, published on 12 May 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
Weakness: CWE-122
Which versions are affected by CVE-2026-42831?
It affects 3 products.
Products include Microsoft 365 Copilot, Microsoft Office, Microsoft Office Long Term Servicing Channel.
How do I fix CVE-2026-42831?
No fix has been published for CVE-2026-42831 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-42831 being exploited?
There is no known exploitation of CVE-2026-42831 in the wild and no public exploit code.
Other vulnerabilities in Microsoft 365 Copilot
- CVE-2026-85885 Microsoft 365 Copilot Elevation of Privilege Vulnerability
- CVE-2026-50517 Microsoft M365 Copilot Remote Code Execution Vulnerability
- CVE-2026-54130 M365 Copilot Information Disclosure Vulnerability
- CVE-2025-60724 GDI+ Remote Code Execution Vulnerability
- CVE-2025-53766 GDI+ Remote Code Execution Vulnerability
Sources
Also known as GHSA-vvc2-cg8v-mmjx.