CVE-2021-34523
Detail
Description
Microsoft Exchange Server Elevation of Privilege 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:
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA: Microsoft Corporation
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
CVSS 2.0 Severity and Vector Strings:
Vector:
(AV:N/AC:L/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 Privilege Escalation Vulnerability
11/03/2021
11/17/2021
Apply updates per vendor instructions.
Weakness Enumeration
CWE-ID
CWE Name
Source
NVD-CWE-noinfo
Insufficient Information
NIST
Change History
18 change records found show changes
Modified Analysis by NIST
8/10/2026 3:59:11 PM
Action
Type
Old Value
New Value
Added
Reference Type
Microsoft Corporation: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523 Types: Patch, Vendor Advisory
CVE Modified by Microsoft Corporation
8/10/2026 12:17:56 PM
Action
Type
Old Value
New Value
Added
Reference
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34523
Removed
Reference
http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html
Removed
Reference
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523
Removed
Reference
https://www.zerodayinitiative.com/advisories/ZDI-21-822/
Removed
Reference Type
http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html Types: Exploit, Third Party Advisory, VDB Entry
Removed
Reference Type
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523 Types: Patch, Vendor Advisory
Removed
Reference Type
https://www.zerodayinitiative.com/advisories/ZDI-21-822/ Types: Third Party Advisory, VDB Entry
Changed
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","lessThan":"15.00.1497.015","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 9","cpes":["cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"15.02.0858.010","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 20","cpes":["cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_20:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"15.01.2242.008","versionType":"custom","status":"affected"}]},{"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":"15.01.2176.012","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":"15.02.0792.013","versionType":"custom","status":"affected"}]}]
[{"vendor":"Microsoft","product":"Microsoft Exchange Server 2013 Cumulative Update 23","platforms":["x64-based Systems"],"versions":[{"version":"15.00.0","lessThan":"15.00.1497.015","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 19","platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"15.01.2176.012","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 20","platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"15.01.2242.008","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 8","platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"15.02.0792.013","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 9","platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"15.02.0858.010","versionType":"custom","status":"affected"}]}]
CVE Modified by CISA-ADP
6/16/2026 11:56:03 PM
Action
Type
Old Value
New Value
Added
SSVC
{"timestamp":"2025-02-04T19:06:53.750452Z","id":"CVE-2021-34523","options":[{"exploitation":"active"},{"automatable":"no"},{"technicalImpact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}
CVE Modified by Microsoft Corporation
6/16/2026 11:56:03 PM
Action
Type
Old Value
New Value
Added
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","lessThan":"15.00.1497.015","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2019 Cumulative Update 9","cpes":["cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.02.0","lessThan":"15.02.0858.010","versionType":"custom","status":"affected"}]},{"vendor":"Microsoft","product":"Microsoft Exchange Server 2016 Cumulative Update 20","cpes":["cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_20:*:*:*:*:*:*"],"platforms":["x64-based Systems"],"versions":[{"version":"15.01.0","lessThan":"15.01.2242.008","versionType":"custom","status":"affected"}]},{"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":"15.01.2176.012","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":"15.02.0792.013","versionType":"custom","status":"affected"}]}]
Modified Analysis by NIST
10/30/2025 3:13:30 PM
Action
Type
Old Value
New Value
Added
Reference Type
CISA-ADP: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523 Types: US Government Resource
CVE Modified by CISA-ADP
10/21/2025 8:17:38 PM
Action
Type
Old Value
New Value
Added
Reference
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523
CVE Modified by CISA-ADP
10/21/2025 4:18:38 PM
Action
Type
Old Value
New Value
Removed
Reference
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523
CVE Modified by CISA-ADP
10/21/2025 3:19:08 PM
Action
Type
Old Value
New Value
Added
Reference
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34523
Modified Analysis by NIST
3/07/2025 3:16:42 PM
Action
Type
Old Value
New Value
Added
CWE
NVD-CWE-noinfo
Removed
CWE
CWE-287
CVE Modified by CVE
11/21/2024 1:10:35 AM
Action
Type
Old Value
New Value
Added
Reference
http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html
Added
Reference
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523
Added
Reference
https://www.zerodayinitiative.com/advisories/ZDI-21-822/
CVE Modified by Microsoft Corporation
5/14/2024 5:13:44 AM
Action
Type
Old Value
New Value
Modified Analysis by NIST
2/13/2024 12:20:51 PM
Action
Type
Old Value
New Value
CVE Modified by Microsoft Corporation
12/28/2023 6:15:41 PM
Action
Type
Old Value
New Value
Changed
Description
Microsoft Exchange Server Elevation of Privilege Vulnerability This CVE ID is unique from CVE-2021-33768, CVE-2021-34470.
Microsoft Exchange Server Elevation of Privilege Vulnerability
Added
CVSS V3.1
Microsoft Corporation AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
CWE Remap by NIST
7/12/2022 1:42:04 PM
Action
Type
Old Value
New Value
Changed
CWE
CWE-269
CWE-287
Modified Analysis by NIST
9/21/2021 1:34:36 PM
Action
Type
Old Value
New Value
Changed
Reference Type
http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html No Types Assigned
http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
CVE Modified by Microsoft Corporation
8/20/2021 2:15:07 PM
Action
Type
Old Value
New Value
Added
Reference
http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html [No Types Assigned]
Initial Analysis by NIST
7/22/2021 10:41:49 AM
Action
Type
Old Value
New Value
Added
CVSS V3.1
NIST AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Added
CVSS V2
NIST (AV:N/AC:L/Au:N/C:P/I:P/A:P)
Added
CWE
NIST CWE-269
Added
CPE Configuration
OR
*cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_20:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*
*cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9:*:*:*:*:*:*
Changed
Reference Type
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523 No Types Assigned
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34523 Patch, Vendor Advisory
Changed
Reference Type
https://www.zerodayinitiative.com/advisories/ZDI-21-822/ No Types Assigned
https://www.zerodayinitiative.com/advisories/ZDI-21-822/ Third Party Advisory, VDB Entry
CVE Modified by Microsoft Corporation
7/19/2021 6:15:08 AM
Action
Type
Old Value
New Value
Added
Reference
https://www.zerodayinitiative.com/advisories/ZDI-21-822/ [No Types Assigned]
Quick Info
CVE Dictionary Entry: CVE-2021-34523 NVD
Published Date: 07/14/2021 NVD
Last Modified: 08/10/2026
Source: Microsoft Corporation
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