CVE-2023-21529KEV · OVERDUECWE-502insecure-deserialization

Microsoft Exchange Server Deserialization of Untrusted Data Vulnerability

High · published February 15, 2023

Patch now

Confirmed exploited, and the score agrees

CVSS calls it high at 8.8. It is confirmed in active exploitation. It sits in the 99.1th percentile for exploit probability.

180
days past CISA
deadline
CVSS v3.1
8.8
EPSS
59%
Percentile
99.1
In the wild
Confirmed
What it is

Microsoft Exchange Server Remote Code Execution Vulnerability

The record
Technical detail
CVSS v3.1
8.8 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.59294 · 99.1th percentile
Weakness
CWE-502 · Deserialization of Untrusted Data
Published
2023-02-15T01:15Z
KEV added
2026-04-13 · due 2026-04-27
Affected products (4)
ProductVersionsFixed in
microsoft/exchange_serverall versions—
microsoft/exchange_serverall versions—
microsoft/exchange_serverall versions—
microsoft/exchange_serverall versions—
References (4)
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 · [email protected]https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529 · af854a3a-2127-422b-91ae-364da2661108https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-21529 · 134c704f-9b21-4f2e-91b3-4a467353bcc0https://www.microsoft.com/en-us/security/blog/2026/04/06/storm-1175-focuses-gaze-on-vulnerable-web-facing-assets-in-high-tempo-medusa-ransomware-operations/ · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 13 APR 00:00Z
    Added to CISA KEV — remediate by Apr 27
    kev
  • 14 FEB 19:33Z
    Microsoft Exchange Server Remote Code Execution Vulnerability
    cvelistv5