cve 2026 55138

The cve 2026 55138 tag covers Microsoft Excel information-disclosure vulnerability updates released on July 14, 2026. Microsoft rated the flaw Medium with a CVSS 3.1 base score of 5.5. The vulnerability can expose sensitive data when a user interacts with malicious content and affects Microsoft 365 Apps for enterprise, Excel 2016, Office 2019, Office LTSC editions, Office for Mac, and Office Online Server. Microsoft has addressed it through the July security updates. The issue was not known to be exploited in the wild when reported, but its broad impact makes the update relevant to managed enterprise fleets and standalone Office installations.