CVEs / CVE-2021-42321
CVE-2021-42321: Microsoft Exchange Server Remote Code Execution Vulnerability
- Known exploited in the CISA KEV catalog since 17 Nov 2021
- medium 6.5 CVSS 2.0 (NVD)
- EPSS 91.7% 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
An authenticated attacker could leverage improper validation in cmdlet arguments within Microsoft Exchange and perform remote code execution.
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 21 | from 15.01.0, before 15.01.2308.020 | 15.01.2308.020 |
| Microsoft Microsoft Exchange Server 2016 Cumulative Update 22 | from 15.0.0, before 15.01.2375.017 | 15.01.2375.017 |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 10 | from 15.02.0, before 15.02.0792.019 | 15.02.0792.019 |
| Microsoft Microsoft Exchange Server 2019 Cumulative Update 11 | from 15.02.0, before 15.02.0986.014 | 15.02.0986.014 |
Exploitation
| In CISA KEV since | 17 Nov 2021 |
|---|---|
| Due date for US federal agencies | 1 Dec 2021 |
| Used in ransomware campaigns | Known |
| Required action | Apply updates per vendor instructions. |
Severity
| CVSS 2.0 | 6.5 mediumAV:N/AC:L/Au:S/C:P/I:P/A:PScored by NVD |
|---|
References
- CVE-2021-42321 on NVD
- CVE-2021-42321 in the CISA KEV catalog
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42321 Patch, Vendor Advisory
- http://packetstormsecurity.com/files/166153/Microsoft-Exchange-Server-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
- http://packetstormsecurity.com/files/168131/Microsoft-Exchange-Server-ChainedSerializationBinder-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42321 Patch, Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42321 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.