Actively exploited
Listed in CISA’s Known Exploited Vulnerabilities catalog since April 13, 2026.
CVE-2023-21529
Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability
Added to KEV April 13, 2026
Alert details
- Source feed
- CISA KEV
- CVE ID
- CVE-2023-21529
- CWE
- CWE-502
- Affected products
- Exchange Server · Microsoft Exchange Server · Microsoft
What happened
Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
What it means for your business
Microsoft Exchange Server is listed in CISA's Known Exploited Vulnerabilities catalog (CVE-2023-21529). Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution. CISA remediation due date: 2026-04-27. If you need help checking exposure, call (864) 335-9223.
Required action
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA due date: April 27, 2026
Sources
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