Vulnerability Intelligence

🛡 CVE-2023-21529

Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability
Microsoft Exchange Server CWE-502

Ransomware use

KNOWN
CISA KEV

EPSS

62.1%
Likely exploited · 99th pct

Added to KEV

2026-04-13
CISA

Remediate by

2026-04-27
⚠ OVERDUE

CWE

CWE-502
weakness
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📈 EPSS exploit probability

62.1%
FIRST EPSS — 30-day probability of exploitation in the wild · band Likely exploited · higher than 99% of all scored CVEs

⚠ KEV remediation overdue

CISA required federal remediation by 2026-04-27. This exploited vulnerability is past its Binding Operational Directive 22-01 due date — prioritize patch/mitigation and hunt for exploitation.

📄 Description

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

🏹 Attributed exploitation

Malware / ransomware (KEV): ransomware (KEV-flagged)

Malware pivots: 🦠 ransomware 🦠 ransomware (KEV-flagged)

🔗 External references & OSINT

NVD →CISA KEV →MITRE CVE →Exploit-DB →EPSS (FIRST) →VulnCheck →Tenable →CVE.org →GitHub PoC →Vulmon →

🔄 Internal pivots & actions

Search this CVE →Correlation graph →Generate detection rules →Timeline →Link analysis →Ransomware theater →

🛡 Add to case

Attach CVE-2023-21529 (Vulnerability / CVE) and pull all linked entities:

🗃 Data Management

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