CVE-2023-21529 Exploited in the Wild — Microsoft Exchange Server 2019 Cumulative Update 12, Microsoft Exchange Server 2019 Cumulative Update 11, Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2016 Cumulative Update 23

Vendor	Product	Version	Status
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 12	15.02.0 to < 15.02.1118.025	Affected
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 11	15.02.0 to < 15.02.0986.041	Affected
Microsoft	Microsoft Exchange Server 2013 Cumulative Update 23	15.00.0 to < 15.00.1497.047	Affected
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 23	15.01.0 to < 15.01.2507.021	Affected

Known Exploited Vulnerability Sources

Catalogues that list this CVE as a known exploited vulnerability.

Per-source evidence links for KEV attestations are available through the KEVIntel Pro API.

Source	Added
CVE First	2026-06-01 13:07 UTC
CISA	2026-06-02 14:02 UTC

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Virtual Patch

Compensating WAF rules to help reduce exposure to this CVE. Rule content and deployable vendor exports are available with KEVIntel Enterprise.

Not available

KEVIntel does not currently have a virtual patch for this CVE. When available, KEVIntel virtual patches ship as deployable ModSecurity, Cloudflare, and AWS WAF rules.

Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to KEVIntel Enterprise users.

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CVSS Scores

CVSS v3.1 8.8 High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation Status

Exploited in the wild

Recorded 2026-06-01 13:07:10 UTC · CVE

Used in malware

Recorded 2026-06-02 14:02:11 UTC · CVE

Weaknesses (CWE)

CWE-502

Deserialization of Untrusted Data

Timeline

Key exploitation, disclosure, scanner coverage, and KEV attestation events for this CVE.

2 Jun 2026 14:02 UTC about 2 months ago

2 Jun 2026 14:02 UTC · about 2 months ago

First public exploitation report

Exploit observed in malware
2 Jun 2026 14:02 UTC about 2 months ago

2 Jun 2026 14:02 UTC · about 2 months ago

Added to CISA KEV

Listed in the CISA Known Exploited Vulnerabilities catalog
1 Jun 2026 13:07 UTC about 2 months ago

1 Jun 2026 13:07 UTC · about 2 months ago

Added to KEVIntel KEV Feed

High-confidence, third-party attested exploitation
14 Feb 2023 19:33 UTC over 3 years ago

14 Feb 2023 19:33 UTC · over 3 years ago

CVE published

Vulnerability disclosed publicly
1 Dec 2022 14:00 UTC over 3 years ago

1 Dec 2022 14:00 UTC · over 3 years ago

CVE ID reserved

Identifier reserved by the CNA

Automate This Intelligence with the Pro API

Confidence scoring, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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Pro API Example

GET /api/v2/pro/kevs/CVE-2023-21529

{
  "cve_id": "CVE-2023-21529",
  "title": "Microsoft Exchange Server Remote Code Execution Vulnerability",
  "affected_vendor": "Microsoft",
  "affected_product": "Microsoft Exchange Server 2019 Cumulative Update 12, Microsoft Exchange Server 2019 Cumulative Update 11, Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2016 Cumulative Update 23",
  "affected_versions": [
    { "vendor": "...", "product": "...", "status": "affected", "display_label": "..." }
  ],
  "confidence": "Confirmed",
  "cvss_score": 8.8,
  "epss_score": 0.62104,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "...": "Pro API fields" },
  "proof_of_concepts": [ "..." ],
  "scanner_integrations": [ "..." ]
}

The free JSON API returns basic KEV fields only. Confidence, telemetry, and artifact enrichment require Pro API access.

CVE-2023-21529

At a Glance

Affected Versions

CVE References

Recommended Actions