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High 7.8Known exploited (CISA KEV)Published Mar 2, 2021
CVE-2021-27065Microsoft Exchange Server Remote Code Execution Vulnerability
Updated under an hour ago ()
Does this affect you?
It affects Microsoft Exchange Server 2013 Cumulative Update 21 and 25 other products. Add what you run to find out whether that includes you.
CISA lists it as known exploited since Nov 3, 2021; federal agencies had to remediate by May 3, 2022, and it is known to be used in ransomware. Treat that date as your deadline.
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Microsoft Exchange Server Remote Code Execution Vulnerability
- CVSS
- 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
- Weakness (CWE)
- CWE-22
- Known exploited
- Added to CISA KEV Nov 3, 2021; federal remediation due May 3, 2022; known ransomware useApply updates per vendor instructions.
- EPSS (exploitation in the next 30 days)
- 99.88% (percentile 100)
- Assigned by
- microsoft
- NVD analysis
- Analyzed
- Record last updated
- Oct 1, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Microsoft Microsoft Exchange Server 2013 Cumulative Update 21 microsoft:exchange_server_2013_cumulative_update_21 (from the name) | from 15.00.0 before 15.00.1395.012 | CNA record |
Microsoft Microsoft Exchange Server 2013 Cumulative Update 22 microsoft:exchange_server_2013_cumulative_update_22 (from the name) | from 15.00.0 before 15.00.1473.006 | CNA record |
Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 microsoft:exchange_server_2013_cumulative_update_23 (from the name) | from 15.00.0 before 15.00.1497.012 | CNA record |
Microsoft Microsoft Exchange Server 2013 Service Pack 1 microsoft:exchange_server_2013_service_pack_1 (from the name) | from 15.00.0 before 15.00.0847.064 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 10 microsoft:exchange_server_2016_cumulative_update_10 (from the name) | from 15.01.0 before 15.01.1531.012 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 11 microsoft:exchange_server_2016_cumulative_update_11 (from the name) | from 15.01.0 before 15.01.1591.018 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 12 microsoft:exchange_server_2016_cumulative_update_12 (from the name) | from 15.01.0 before 15.01.1713.010 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 13 microsoft:exchange_server_2016_cumulative_update_13 (from the name) | from 15.01.0 before 15.01.1779.008 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 14 microsoft:exchange_server_2016_cumulative_update_14 (from the name) | from 15.01.0 before 15.01.1847.012 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 15 microsoft:exchange_server_2016_cumulative_update_15 (from the name) | from 15.01.0 before 15.01.1913.012 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 16 microsoft:exchange_server_2016_cumulative_update_16 (from the name) | from 15.01.0 before 15.01.1979.008 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 17 microsoft:exchange_server_2016_cumulative_update_17 (from the name) | from 15.01.0 before 15.01.2044.013 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 18 microsoft:exchange_server_2016_cumulative_update_18 (from the name) | from 15.01.0 before 15.01.2106.013 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 19 microsoft:exchange_server_2016_cumulative_update_19 (from the name) | from 15.01.0 before 15.01.2176.009 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 8 microsoft:exchange_server_2016_cumulative_update_8 (from the name) | from 15.01.0 before 15.01.1415.010 | CNA record |
Microsoft Microsoft Exchange Server 2016 Cumulative Update 9 microsoft:exchange_server_2016_cumulative_update_9 (from the name) | from 15.01.0 before 15.01.1466.016 | CNA record |
Microsoft Microsoft Exchange Server 2019 microsoft:exchange_server_2019 (from the name) | from 15.02.0 before 15.02.0221.018 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 1 microsoft:exchange_server_2019_cumulative_update_1 (from the name) | 15.02.0 builds before 15.01.1979.006 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 2 microsoft:exchange_server_2019_cumulative_update_2 (from the name) | from 15.02.0 before 15.02.0397.011 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 3 microsoft:exchange_server_2019_cumulative_update_3 (from the name) | from 15.02.0 before 15.02.0464.015 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 4 microsoft:exchange_server_2019_cumulative_update_4 (from the name) | from 15.02.0 before 15.02.0659.012 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 5 microsoft:exchange_server_2019_cumulative_update_5 (from the name) | from 15.02.0 before 15.02.0595.008 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 6 microsoft:exchange_server_2019_cumulative_update_6 (from the name) | from 15.02.0 before 15.02.0529.013 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 7 microsoft:exchange_server_2019_cumulative_update_7 (from the name) | from 15.02.0 before 15.02.0721.013 | CNA record |
Microsoft Microsoft Exchange Server 2019 Cumulative Update 8 microsoft:exchange_server_2019_cumulative_update_8 (from the name) | from 15.02.0 before 15.02.0792.010 | CNA record |
microsoft exchange_server microsoft:exchange_server | 2013; 2013; 2013; 2013; 2016; 2016; 2016; 2016; and 16 more ranges | NVD |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-27065vendor-advisory, patch
- http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.htmlexploit, third-party-advisory, vdb-entry
- http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.htmlexploit, third-party-advisory, vdb-entry
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-27065patch, vendor-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27065us-government-resource
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.