CVE-2021-26857
Detail
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Metrics
CVSS Version 4.0
CVSS Version 3.x
CVSS Version 2.0
NVD enrichment efforts reference publicly available information to associate
vector strings. CVSS information contributed by other sources is also
displayed.
CVSS 4.0 Severity and Vector Strings:
NVD assessment
not yet provided.
CVSS 3.x Severity and Vector Strings:
CNA: Microsoft Corporation
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS 2.0 Severity and Vector Strings:
Vector:
(AV:N/AC:M/Au:N/C:P/I:P/A:P)
References to Advisories, Solutions, and Tools
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This CVE is in CISA's Known Exploited Vulnerabilities Catalog
Reference
CISA's BOD 22-01 and Known
Exploited Vulnerabilities Catalog for further guidance and requirements.
Vulnerability Name
Date Added
Due Date
Required Action
Microsoft Exchange Server Remote Code Execution Vulnerability
11/03/2021
05/03/2022
Apply updates per vendor instructions.
Weakness Enumeration
CWE-ID
CWE Name
Source
CWE-502
Deserialization of Untrusted Data
NIST
CISA-ADP
Change History
18 change records found show changes
Modified Analysis by NIST
8/19/2026 3:22:27 PM
Action
Type
Old Value
New Value
Changed
CPE Configuration
Record truncated, showing 2048 of 2064 characters.
View Entire Change Record OR
*cpe:2.3:a:microsoft:exchange_server:2010:sp3:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:sp1:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_8:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_9:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_22:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_1:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_2:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_14:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_3:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_4:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_15:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:-:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_6:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_5:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_17:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_16:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_updat
Record truncated, showing 2048 of 2149 characters.
View Entire Change Record OR
*cpe:2.3:a:microsoft:exchange_server:2010:sp3:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:sp1:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_8:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_9:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_21:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_22:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_1:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_2:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_14:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_3:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_4:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_15:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:-:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_6:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_5:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_17:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_16:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_upda
Added
Reference Type
Microsoft Corporation: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26857 Types: Patch, Vendor Advisory
CVE Modified by Microsoft Corporation
8/19/2026 1:17:38 PM
Action
Type
Old Value
New Value
Added
Reference
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-26857
Removed
Reference
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857
Removed
Reference Type
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857 Types: Patch, Vendor Advisory
Changed
Affected
Record truncated, showing 2048 of 7936 characters.
View Entire Change Record [{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 19","cpes":["cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 8","cpes":["cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019","cpes":["cpe:2.3:a:microsoft:exchange_server:2019:*:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 22","cpes":["cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_22:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.00.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 2","cpes":["cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_2:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 13","cpes":["cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 23","cpes":["cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.00.0"
Record truncated, showing 2048 of 5827 characters.
View Entire Change Record [{"vendor":"Microsoft","product":"Microsoft Exchange Server 2010 Service Pack 3","versions":[{"version":"14.0.0.0","lessThan":"14.03.0513.000","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 21","platforms":["x64-based Systems"],"versions":[{"version":"15.00.0","lessThan":"15.00.1395.012","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 22","platforms":["x64-based Systems"],"versions":[{"version":"15.00.0","lessThan":"15.00.1473.006","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 23","platforms":["x64-based Systems"],"versions":[{"version":"15.00.0","lessThan":"15.00.1497.012","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Service Pack 1","platforms":["x64-based Systems"],"versions":[{"version":"15.00.0","lessThan":"15.00.0847.064","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 10","platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"15.01.1531.012","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 11","platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"15.01.1591.018","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 12","platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"15.01.1713.010","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 13","platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"15.01.1779.008","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchan
CVE Modified by CISA-ADP
8/12/2026 1:17:39 AM
Action
Type
Old Value
New Value
Changed
SSVC
{"timestamp":"2024-12-04T17:23:38.395840Z","id":"CVE-2021-26857","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}
{"timestamp":"2021-03-02T00:00:00+00:00","id":"CVE-2021-26857","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}
CVE Modified by CISA-ADP
6/16/2026 11:43:51 PM
Action
Type
Old Value
New Value
Added
SSVC
{"timestamp":"2024-12-04T17:23:38.395840Z","id":"CVE-2021-26857","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}
CVE Modified by Microsoft Corporation
6/16/2026 11:43:51 PM
Action
Type
Old Value
New Value
Added
Affected
Record truncated, showing 2048 of 7936 characters.
View Entire Change Record [{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 19","cpes":["cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 8","cpes":["cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019","cpes":["cpe:2.3:a:microsoft:exchange_server:2019:*:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 22","cpes":["cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_22:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.00.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 2","cpes":["cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_2:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 13","cpes":["cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"publication","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 23","cpes":["cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.00.0"
CVE CISA KEV Update by Cybersecurity and Infrastructure Security Agency (CISA) U.S. Civilian Government
12/17/2025 9:00:03 PM
Action
Type
Old Value
New Value
Changed
Due Date
2021-04-16
2022-05-03
Modified Analysis by NIST
10/30/2025 3:55:52 PM
Action
Type
Old Value
New Value
Added
Reference Type
CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26857 Types: US Government Resource
CVE Modified by CISA-ADP
10/21/2025 8:17:28 PM
Action
Type
Old Value
New Value
Added
Reference
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26857
CVE Modified by CISA-ADP
10/21/2025 4:18:25 PM
Action
Type
Old Value
New Value
Removed
Reference
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26857
CVE Modified by CISA-ADP
10/21/2025 3:18:57 PM
Action
Type
Old Value
New Value
Added
Reference
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26857
Modified Analysis by NIST
3/07/2025 10:37:26 AM
Action
Type
Old Value
New Value
CVE Modified by CISA-ADP
2/04/2025 3:15:41 PM
Action
Type
Old Value
New Value
Added
CWE
CWE-502
CVE Modified by CVE
11/21/2024 12:56:54 AM
Action
Type
Old Value
New Value
Added
Reference
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857
Modified Analysis by NIST
7/25/2024 1:53:21 PM
Action
Type
Old Value
New Value
Changed
CPE Configuration
OR
*cpe:2.3:a:microsoft:exchange_server:2010:sp3:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*
OR
*cpe:2.3:a:microsoft:exchange_server:2010:sp3:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_22:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:sp1:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_14:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_15:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_16:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_17:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_8:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_9:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:-:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_1:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_2:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_3:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_4:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_5:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_6:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*
CVE Modified by Microsoft Corporation
5/14/2024 4:36:45 AM
Action
Type
Old Value
New Value
CVE Modified by Microsoft Corporation
12/29/2023 12:16:01 PM
Action
Type
Old Value
New Value
Changed
Description
Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-26412, CVE-2021-26854, CVE-2021-26855, CVE-2021-26858, CVE-2021-27065, CVE-2021-27078.
Microsoft Exchange Server Remote Code Execution Vulnerability
Added
CVSS V3.1
Microsoft Corporation AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE Remap by NIST
7/12/2022 1:42:04 PM
Action
Type
Old Value
New Value
Changed
CWE
NVD-CWE-noinfo
CWE-502
Initial Analysis by NIST
3/08/2021 3:45:32 PM
Action
Type
Old Value
New Value
Added
CVSS V3.1
NIST AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Added
CVSS V2
NIST (AV:N/AC:M/Au:N/C:P/I:P/A:P)
Added
CWE
NIST NVD-CWE-noinfo
Added
CPE Configuration
OR
*cpe:2.3:a:microsoft:exchange_server:2010:sp3:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*
Changed
Reference Type
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857 No Types Assigned
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26857 Patch, Vendor Advisory
Added
CVSS V2 Metadata
Victim must voluntarily interact with attack mechanism
Quick Info
CVE Dictionary Entry: CVE-2021-26857 NVD
Published Date: 03/02/2021 NVD
Last Modified: 08/19/2026
Source: Microsoft Corporation
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