CVE-2021-26855

CRITICAL severity · CVSS 9.1 · Server-side request forgery (SSRF) · actively exploited (CISA KEV)

9.1CVSS CRITICAL ● exploited ⚠ ransomware

🔴 Actively exploited in the wild (CISA Known Exploited Vulnerabilities). ⚠ Known use in ransomware campaigns. Added to KEV 2021-11-03. US federal agencies must patch by 2022-05-03.

Summary

Microsoft Exchange Server Remote Code Execution Vulnerability

Impact & exploitability

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

Confidentiality impactHigh

Integrity impactHigh

Availability impactNone

Exploit probability (EPSS)94%

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products we track (1)

Microsoft Exchange Server

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://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855 ↗

CVE-2021-26855

Summary

Impact & exploitability

Affected products we track (1)

Recommendation

Additional information