CVE-2026-55040
CRITICAL severity · CVSS 9.1 · CWE-1390 · actively exploited (CISA KEV)
9.1CVSS CRITICAL exploited
Actively exploited in the wild (CISA Known Exploited Vulnerabilities).
Added to KEV 2026-08-18. US federal agencies must patch by 2026-08-21.
Summary
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
Impact & exploitability
Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
Confidentiality impactHigh
Integrity impactHigh
Availability impactNone
Exploit probability (EPSS)4%
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Affected products we track (1)
Recommendation
This vulnerability is being actively exploited in the wild — patch affected products urgently. Open any affected product above for its exact safe version.
Official patch: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55040 ↗