Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability

Technical Severity

CVSS v3.1 Metrics

HIGH

8.8 / 10

Minimal Risk Critical

Vector Specification

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

Exploitation Likelihood

EPSS Prediction

28.94 %

Predictive Probability

Percentile Rank

96.6 th

Documented as more likely to be exploited than 96.6% of known CVEs.

Detection Date

Apr 13, 2026

Remediation Due

Apr 27, 2026

CISA Catalog Active

Threat Analysis

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

Remediation Directive

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

External Intelligence

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529

NVD

National Vulnerability Database

https://nvd.nist.gov/vuln/detail/CVE-2023-21529