CVE-2023-21529: listed in the CISA KEV catalog

CVE-2023-21529 · CVSS 8.8 HIGH · EPSS 62% · KEV 2026-04-13

Microsoft Exchange Server Remote Code Execution Vulnerability

Is CVE-2023-21529 exploited?

• Listed in the CISA KEV catalog on 2026-04-13.
• Federal remediation due 2026-04-27.
• Past that date by 110 days.
• EPSS puts exploitation in the next 30 days at 62%.
• Public exploit code: none found in monitored sources.

Which products and versions are affected?

No affected package list recorded here yet.

Is there a patch?

No patch identifier recorded here yet.

What PlainSec published about CVE-2023-21529

• Attackers Exploit Both Decade-Old and New Flaws in Federal Systems (2026-04-08)

Primary sources

• NVD record
• CISA KEV catalog

What this record does not say

• No affected package data.
• No patch identifier.

KEV and EPSS are re-checked daily. Record last updated 2026-08-11.