High 8.8Known exploited (CISA KEV)Published Feb 14, 2023

CVE-2023-21529Microsoft Exchange Server Remote Code Execution Vulnerability

Updated under an hour ago (Oct 27, 2026, 11:00 AM ET)

Does this affect you?

It affects Microsoft Exchange Server 2013 Cumulative Update 23 and 4 other products. Add what you run to find out whether that includes you.

CISA lists it as known exploited since Apr 13, 2026; federal agencies had to remediate by Apr 27, 2026, and it is known to be used in ransomware. Treat that date as your deadline.

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Every CVE for Microsoft Exchange Server 2013 Cumulative Update 23

Exploited in the last 30 days

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS: 8.8 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Weakness (CWE): CWE-502
Known exploited: Added to CISA KEV Apr 13, 2026; federal remediation due Apr 27, 2026; known ransomware useApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
EPSS (exploitation in the next 30 days): 59.29% (percentile 99)
Assigned by: microsoft
NVD analysis: Analyzed
Record last updated: Aug 19, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 microsoft:exchange_server_2013_cumulative_update_23 (from the name)	from 15.00.0 before 15.00.1497.047	CNA record
Microsoft Microsoft Exchange Server 2016 Cumulative Update 23 microsoft:exchange_server_2016_cumulative_update_23 (from the name)	from 15.01.0 before 15.01.2507.021	CNA record
Microsoft Microsoft Exchange Server 2019 Cumulative Update 11 microsoft:exchange_server_2019_cumulative_update_11 (from the name)	from 15.02.0 before 15.02.0986.041	CNA record
Microsoft Microsoft Exchange Server 2019 Cumulative Update 12 microsoft:exchange_server_2019_cumulative_update_12 (from the name)	from 15.02.0 before 15.02.1118.025	CNA record
microsoft exchange_server microsoft:exchange_server	2013; 2016; 2019; 2019	NVD

References

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529	vendor-advisory, patch
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-21529	us-government-resource
https://www.microsoft.com/en-us/security/blog/2026/04/06/storm-1175-focuses-gaze-on-vulnerable-web-facing-assets-in-high-tempo-medusa-ransomware-operations/	technical-description

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.