9 Realms Cybersecurity
AdvisoriesCVE-2023-21529

Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability

MicrosoftExchange ServerAdded April 13, 2026

CISA Known Exploited Vulnerabilities Data

Description

Microsoft Exchange Server contains a deserialization of untrusted data that allows an authenticated attacker to achieve remote code execution.

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 (federal agency requirement)

Known Ransomware Campaign Use

Unknown

Notes

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 ; https://nvd.nist.gov/vuln/detail/CVE-2023-21529

External References

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Data sourced from the CISA Known Exploited Vulnerabilities catalog. CISA does not endorse any commercial product or service.