CVE-2023-21529
Act now ● On CISA KEV — actively exploited used in ransomware
Actively exploited — on the CISA KEV list.
CVSS base
8.8
HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS — probability of exploitation (30 days)
62.1%
99.1th percentile
CISA KEV
Listed
Added 2026-04-13 · patch by 2026-04-27
Weakness / dates
CWE-502
Published 2023-02-14 · modified 2026-08-19
CVSS breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
| Attack Vector | N | Network |
| Attack Complexity | L | Low |
| Privileges Required | L | Low |
| User Interaction | N | None |
| Scope | U | Unchanged |
| Confidentiality | H | High |
| Integrity | H | High |
| Availability | H | High |
Timeline
- 2023-02-14 — Published (NVD)
- 2026-04-13 — Added to CISA KEV (actively exploited)
- 2026-04-27 — CISA patch-by deadline
- 2026-08-19 — Last modified (NVD)
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Affected
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2023-21529
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-21529
- https://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/