AI analysis
CVE-2026-97742 is a stack-based buffer overflow (CWE-121) in Microsoft Office Excel. A remote attacker can trigger it by getting a user to open a crafted workbook; no prior privileges are required, but user interaction is required. Successful exploitation allows arbitrary code execution in the context of the user who opened the file, with high impact to confidentiality, integrity, and availability. Affected products named in the advisory data are Microsoft 365 Apps, Microsoft 365, Office 2021, Office 2024, and Office Online Server. It is not on CISA's Known Exploited Vulnerabilities list, and no public proof-of-concept is known.
What to do: Install Microsoft's October 2026 security updates for Microsoft 365 Apps, Microsoft 365, Office 2021, Office 2024, and Office Online Server as soon as they are available. Until patches are deployed, do not open Excel workbooks from untrusted sources, and use Protected View or Application Guard where it is already enabled.
Affected
| Microsoft 365 Apps | Affected releases as listed for CVE-2026-97742 (no numeric builds in the advisory data) |
| Microsoft 365 | Affected releases as listed for CVE-2026-97742 (no numeric builds in the advisory data) |
| Microsoft Office 2021 | Affected releases as listed for CVE-2026-97742 (no numeric builds in the advisory data) |
| Microsoft Office 2024 | Affected releases as listed for CVE-2026-97742 (no numeric builds in the advisory data) |
| Microsoft Office Online Server | Affected releases as listed for CVE-2026-97742 (no numeric builds in the advisory data) |
Estimated exposure
massOn the order of 100 million or more Office and Microsoft 365 users — Microsoft 365 and Office are deployed across consumer and enterprise desktops worldwide, with public subscriber figures well above 100 million; this is an order-of-magnitude estimate, not a count of vulnerable installs.