Remote code execution in Microsoft Word affecting Microsoft 365 and Office versions; widely used enterprise software with potential for broad impact.
CVE-2026-83891
Remote code execution in Microsoft Word via stack-based buffer overflow.
Is CVE-2026-83891 being exploited?
Not confirmed. CVE-2026-83891 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.77% probability of exploitation in the next 30 days.
How severe is CVE-2026-83891?
CVE-2026-83891 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-83891?
Yes. A fix has been recorded for CVE-2026-83891. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-83891 affect?
CVE-2026-83891 affects Microsoft 365 Apps, Microsoft 365, Microsoft Office 2021, Microsoft Office 2024. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-83891?
Apply Microsoft security update immediately; block untrusted docs and enable Protected View.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote attackers can execute arbitrary code by delivering a crafted document, potentially achieving full system compromise under victim context.
Immediate action required
- affected>= 16.0.1 and < https://aka.ms/OfficeSecurityReleases
- affected>= 1.0.0 and < publication
- affected>= 16.0.1 and < 16.0.14334.20974
- affected>= 16.0.0 and < 16.0.17932.21056
- affected>= 16.0.1 and < publication
- affected>= 16.0.0 and < publication
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.