CVE-2021-34523
CRITICAL severity · CVSS 9 · actively exploited (CISA KEV)
9CVSS 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 2021-11-17.
Summary
Microsoft Exchange Server Elevation of Privilege Vulnerability
Impact & exploitability
Attack vectorLocal
Attack complexityLow
Privileges requiredNone
User interactionNone
Confidentiality impactHigh
Integrity impactHigh
Availability impactNone
Exploit probability (EPSS)94%
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/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://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523 ↗
Additional information
- NVD record
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523Patch
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523Patch
- https://www.zerodayinitiative.com/advisories/ZDI-21-822/Advisory
- https://www.zerodayinitiative.com/advisories/ZDI-21-822/Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523
- http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.htmlAdvisory
- http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.htmlAdvisory