CVE-2021-42321
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)
91.7%
99.8th percentile
CISA KEV
Listed
Added 2021-11-17 · patch by 2021-12-01
Weakness / dates
—
Published 2021-11-10 · 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
- 2021-11-10 — Published (NVD)
- 2021-11-17 — Added to CISA KEV (actively exploited)
- 2021-12-01 — 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-2021-42321
- exploit http://packetstormsecurity.com/files/166153/Microsoft-Exchange-Server-Remote-Code-Execution.html
- exploit http://packetstormsecurity.com/files/168131/Microsoft-Exchange-Server-ChainedSerializationBinder-Remote-Code-Execution.html
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42321
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42321