CVEs / CVE-2021-34523
CVE-2021-34523: Microsoft Exchange Server Privilege Escalation Vulnerability
- Known exploited in the CISA KEV catalog since 3 Nov 2021
- high 7.5 CVSS 2.0 (NVD)
- EPSS 99.9% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
Microsoft Exchange Server contains an unspecified vulnerability that allows for privilege escalation.
Description
Microsoft Exchange Server Elevation of Privilege Vulnerability
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 | from 15.00.0, before 15.00.1497.015 | 15.00.1497.015 |
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 19 | from 15.01.0, before 15.01.2176.012 | 15.01.2176.012 |
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 20 | from 15.01.0, before 15.01.2242.008 | 15.01.2242.008 |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 8 | from 15.02.0, before 15.02.0792.013 | 15.02.0792.013 |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 9 | from 15.02.0, before 15.02.0858.010 | 15.02.0858.010 |
Exploitation
| In CISA KEV since | 3 Nov 2021 |
|---|---|
| Due date for US federal agencies | 17 Nov 2021 |
| Used in ransomware campaigns | Known |
| Required action | Apply updates per vendor instructions. |
Severity
| CVSS 2.0 | 7.5 highAV:N/AC:L/Au:N/C:P/I:P/A:PScored by NVD |
|---|
References
- CVE-2021-34523 on NVD
- CVE-2021-34523 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523 Patch, Vendor Advisory
- http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523 Patch, Vendor Advisory
- https://www.zerodayinitiative.com/advisories/ZDI-21-822/ Third Party Advisory, VDB Entry
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523 US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.