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High 7.8Known exploited (CISA KEV)Published Mar 2, 2021
CVE-2021-26857Microsoft Exchange Server Remote Code Execution Vulnerability
Updated under an hour ago ()
Does this affect you?
It affects Microsoft Exchange Server 2010 Service Pack 3 and 26 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-502
- 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)
- 95.76% (percentile 100)
- Assigned by
- microsoft
- NVD analysis
- Analyzed
- Record last updated
- Aug 19, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Microsoft Microsoft Exchange Server 2010 Service Pack 3 microsoft:exchange_server_2010_service_pack_3 (from the name) | from 14.0.0.0 before 14.03.0513.000 | CNA record |
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 | 2010; 2013; 2013; 2013; 2013; 2016; 2016; 2016; and 18 more ranges | NVD |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26857vendor-advisory, patch
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857patch, vendor-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26857us-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.