CVE-2021-34523
KEVRansomware UseMicrosoft Exchange Server Privilege Escalation Vulnerability
Description
Microsoft Exchange Server contains an unspecified vulnerability that allows for privilege escalation.
Microsoft Exchange Server Elevation of Privilege Vulnerability
CVSS 3.1 vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:NPublishedJul 14, 2021
Last modifiedAug 10, 2026
Added to KEVNov 3, 2021
Remediation dueNov 17, 2021
References
- msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523PatchVendor Advisory
- packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.htmlExploitThird Party Advisory
- portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523PatchVendor Advisory
- zerodayinitiative.com/advisories/ZDI-21-822/Third Party AdvisoryVDB Entry
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523US Government Resource
0 recent articles mention this CVE
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Risk assessment · Critical
Actively exploited and used by ransomware crews. Patch immediately.
- Exploitation
- Confirmed in the wild (CISA KEV)
- Federal remediation deadline
- Overdue by 1805 days
- Ransomware
- Used in known ransomware campaigns
- CVSS
- 9.0 CRITICAL
- EPSS (30-day exploit probability)
- 100.0% · top 1% of all CVEs
- Weakness
- NVD-CWE-noinfo
- Preconditions
- No privileges and no user interaction
Recommended actions
- 1.Apply updates per vendor instructions.
- 2.Treat as emergency change: patch or isolate internet-facing instances first.
- 3.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
- 4.Verify offline/immutable backups and segment the affected systems. This flaw is used for ransomware initial access.
Assessment is derived automatically from the live signals above; verify against your own asset inventory.