CVE-2021-34523 KEV
9.0
CRITICAL · CVSS 3.1 · EPSS 100% (pctl 100)
Patch first
On CISA KEV — known exploited in the wild, due 2021-11-17.
Description
Microsoft Exchange Server Elevation of Privilege Vulnerability
Scoring
| CVSS | 9.0 (CRITICAL, v3.1) |
|---|---|
| Vector | CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N |
| EPSS | 99.99% — more likely to be exploited than 100% of all CVEs |
| On CISA KEV | yes — remediate by 2021-11-17 |
| Public exploit | none known |
| Published | 2021-07-14 |
| Last modified | 2026-08-10 |
CISA KEV
| Name | Microsoft Exchange Server Privilege Escalation Vulnerability |
|---|---|
| Added | 2021-11-03 |
| Due | 2021-11-17 |
| Vendor / product | Microsoft / Exchange Server |
| Ransomware use | known |
Affected (1)
| Vendor | Product |
|---|---|
| microsoft | exchange server |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523
- http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523
- https://www.zerodayinitiative.com/advisories/ZDI-21-822/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523
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