[ CVE-2023-21529 · Published 14 Feb 2023 ]
Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability
Exploited · CISA KEV CVSS 8.8
EPSS 59%Fix available
[ Why it matters ]Priority signals
- Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2026-04-13
- Known to be used in ransomware campaigns
- EPSS: 59% chance of exploitation in the next 30 days (higher than 99% of CVEs)
[ Description ]Official description
Microsoft Exchange Server Remote Code Execution Vulnerability
CISA: Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.
[ Fixes ]Fixes and patches
CISA required action (US federal deadline 27 Apr 2026): Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- Patch on msrc.microsoft.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD
[ References ]References
- msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529PatchVendor Advisory
- www.cisa.gov/known-exploited-vulnerabilities-catalogUS Government Resource
- www.microsoft.com/en-us/security/blog/2026/04/06/storm-1175-focuses-gaze-on-vulnerable-…Technical Description