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TI-2021-13502 Aliases CVE-2021-34473GHSA-fgq9-p33g-xcfc

Microsoft Exchange Server Remote Code Execution Vulnerability

Priority CRITICAL 100Exploited in the wildCWE-918Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Microsoft. Impact type from Microsoft.

Summary

Microsoft Exchange Server Remote Code Execution Vulnerability

Why it matters now

Exploitation Active In CISA KEV since 2021-11-03CISA due date 2021-11-17Known ransomware use
EPSS 0.99999 99th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed Microsoft: 1 update

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Active
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MicrosoftMicrosoft Exchange Server 2013 Cumulative Update 2315.00.0 to before 15.00.1497.01515.00.1497.015Patch availableCNA
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 1915.01.0 to before 15.01.2176.01215.01.2176.012Patch availableCNA
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 2015.01.0 to before 15.01.2242.00815.01.2242.008Patch availableCNA
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 815.02.0 to before 15.02.0792.01315.02.0792.013Patch availableCNA
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 915.02.0 to before 15.02.0858.01015.02.0858.010Patch availableCNA
  • Microsoft Exchange Server 2013 Cumulative Update 23 VendorMicrosoft Affected 15.00.0 to before 15.00.1497.015 Fixed in 15.00.1497.015 Patch available CNA
  • Microsoft Exchange Server 2016 Cumulative Update 19 VendorMicrosoft Affected 15.01.0 to before 15.01.2176.012 Fixed in 15.01.2176.012 Patch available CNA
  • Microsoft Exchange Server 2016 Cumulative Update 20 VendorMicrosoft Affected 15.01.0 to before 15.01.2242.008 Fixed in 15.01.2242.008 Patch available CNA
  • Microsoft Exchange Server 2019 Cumulative Update 8 VendorMicrosoft Affected 15.02.0 to before 15.02.0792.013 Fixed in 15.02.0792.013 Patch available CNA
  • Microsoft Exchange Server 2019 Cumulative Update 9 VendorMicrosoft Affected 15.02.0 to before 15.02.0858.010 Fixed in 15.02.0858.010 Patch available CNA

CPE configurations NVD · 5

CPEVersionsRoleVendor
cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*2013 cumulative_update_23VulnerableMicrosoft
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*2016 cumulative_update_19VulnerableMicrosoft
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_20:*:*:*:*:*:*2016 cumulative_update_20VulnerableMicrosoft
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*2019 cumulative_update_8VulnerableMicrosoft
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9:*:*:*:*:*:*2019 cumulative_update_9VulnerableMicrosoft
  • cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:* Versions 2013 cumulative_update_23 Vulnerable ·Microsoft
  • cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:* Versions 2016 cumulative_update_19 Vulnerable ·Microsoft
  • cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_20:*:*:*:*:*:* Versions 2016 cumulative_update_20 Vulnerable ·Microsoft
  • cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:* Versions 2019 cumulative_update_8 Vulnerable ·Microsoft
  • cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_9:*:*:*:*:*:* Versions 2019 cumulative_update_9 Vulnerable ·Microsoft

Remediation

Microsoft 1 update

  • KB5001779
    Security Update
    • Microsoft Exchange Server 2013 Cumulative Update 23 15.00.1497.015
    • Microsoft Exchange Server 2016 Cumulative Update 19 15.01.2176.012
    • Microsoft Exchange Server 2016 Cumulative Update 20 15.01.2242.008
    • Microsoft Exchange Server 2019 Cumulative Update 8 15.02.0792.013
    • Microsoft Exchange Server 2019 Cumulative Update 9 15.02.0858.010

Vendor assessments

Microsoft

Microsoft's page for this CVE →

Impact
Remote Code Execution
Exploited
No
Publicly disclosed
Yes
Exploitability
Exploitation More Likely

Timeline

  1. 2021-11-03 Added to CISA KEV
  2. 2026-10-02 Threatist record created from CVE-2021-34473
  3. 2026-10-03 Alias added: GHSA-fgq9-p33g-xcfc

References

Exploit 1

Patch 2

Advisory 1

  • TI-2024-14170 Microsoft Exchange Server Elevation of Privilege Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2022-19610 Microsoft Exchange Server Elevation of Privilege Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2021-13547 Microsoft Exchange Server Elevation of Privilege Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2021-08465 Microsoft Exchange Server Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2023-07929 Microsoft Exchange Server Remote Code Execution Vulnerability KEVCVSS 3.1HIGH 8.8
  • TI-2022-19581 Microsoft Exchange Server Elevation of Privilege Vulnerability KEVCVSS 3.1HIGH 8.8
See all 258 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences