How severe is CVE-2023-21529?

CVE-2023-21529 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2023-21529 being actively exploited?

Yes. CVE-2023-21529 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2026-04-13, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2023-21529?

CVE-2023-21529 primarily affects Microsoft Exchange Server. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-21529?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2023-21529 have an EU (EUVD) identifier?

Yes. CVE-2023-21529 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2023-25697. It is also flagged as exploited in the EUVD (since 2026-04-13).

When was CVE-2023-21529 published?

CVE-2023-21529 was published on 2023-02-14 and last updated on 2026-08-19.

CVE-2023-21529

CVE-2023-21529 is a high-severity vulnerability in Microsoft Exchange Server with a CVSS 3.x base score of 8.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2026-04-13). The underlying weakness is classified as CWE-502.

Key facts

Severity: High (CVSS 3.x base score 8.8)
EPSS exploit prediction: 62% (99th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2026-04-13)
EU (EUVD) id: EUVD-2023-25697
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2026-04-13)
Weakness: CWE-502
Affected product: Microsoft Exchange Server
Published: 2023-02-14
Last modified: 2026-08-19

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

Frequently asked questions

What is CVE-2023-21529?: Microsoft Exchange Server Remote Code Execution Vulnerability
How severe is CVE-2023-21529?: CVE-2023-21529 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2023-21529 being actively exploited?: Yes. CVE-2023-21529 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2026-04-13, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2023-21529?: CVE-2023-21529 primarily affects Microsoft Exchange Server. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-21529?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2023-21529 have an EU (EUVD) identifier?: Yes. CVE-2023-21529 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2023-25697. It is also flagged as exploited in the EUVD (since 2026-04-13).
When was CVE-2023-21529 published?: CVE-2023-21529 was published on 2023-02-14 and last updated on 2026-08-19.

References

Affected products (4)

cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_23:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_11:*:*:*:*:*:*
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_12:*:*:*:*:*:*

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