RCE in Microsoft Excel — widely used enterprise software; successful exploit can enable widespread compromise and malware spread.
CVE-2026-77902
Heap overflow in Excel enables remote code execution via crafted spreadsheet
Is CVE-2026-77902 being exploited?
Not confirmed. CVE-2026-77902 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 0.80% probability of exploitation in the next 30 days.
How severe is CVE-2026-77902?
CVE-2026-77902 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-2026-77902?
Yes. A fix has been recorded for CVE-2026-77902. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-77902 affect?
CVE-2026-77902 affects Microsoft Excel (Microsoft Office), Microsoft Office for Windows. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-77902?
Apply Microsoft security update immediately; block/disable preview of untrusted Office files
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution: attacker can run arbitrary code when a user opens or previews a malicious Excel file, enabling malware, data theft, and lateral movement.
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.