CVE-2021-34523
Microsoft Exchange Server Privilege Escalation Vulnerability
CVSS
9.0
Critical
EPSS
100.0%
p100
KEV
YES
Nov 3, 2021
Exploit Today
80
0-100
Published: Jul 14, 2021 · Last modified: Aug 10, 2026
100.0%EPSS · 30 days100.0%
2026-09-162026-10-14
Product
Microsoft / Exchange Server
Vulnerability
Microsoft Exchange Server Privilege Escalation Vulnerability
Added to KEV
Nov 3, 2021
Remediate by
Nov 17, 2021
Known ransomware use
Yes
Summary description
Microsoft Exchange Server contains an unspecified vulnerability that allows for privilege escalation.
Required action
Apply updates per vendor instructions.
Notes
https://nvd.nist.gov/vuln/detail/CVE-2021-34523
Microsoft Exchange Server Elevation of Privilege Vulnerability
- msrc.microsoft.comhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523
- packetstormsecurity.comhttp://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html
- portal.msrc.microsoft.comhttps://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523
- www.zerodayinitiative.comhttps://www.zerodayinitiative.com/advisories/ZDI-21-822/
- www.cisa.govhttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523
CVECVSSEPSSKEVRExploitTitleMod.
CVE-2023-215298.8 HIG99.1%
KEV—80Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability57dCVE-2022-410808.8 HIG99.6%
KEV—80Microsoft Exchange Server Privilege Escalation Vulnerability66dCVE-2021-344739.1 CRI100.0%
KEV—80Microsoft Exchange Server Remote Code Execution Vulnerability65dCVE-2021-337667.3 HIG99.9%
KEV—80Microsoft Exchange Server Information Disclosure65dCVE-2021-311967.2 HIG99.0%
KEV—80Microsoft Exchange Server Information Disclosure Vulnerability65dCVE-2021-270657.8 HIG100.0%
KEV—80Microsoft Exchange Server Remote Code Execution Vulnerability13d