CVE-2021-42321 KEV
8.8
HIGH · CVSS 3.1 · EPSS 91.7% (pctl 100)
Patch first
On CISA KEV — known exploited in the wild, due 2021-12-01.
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
Scoring
| CVSS | 8.8 (HIGH, v3.1) |
|---|---|
| Vector | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| EPSS | 91.74% — more likely to be exploited than 100% of all CVEs |
| On CISA KEV | yes — remediate by 2021-12-01 |
| Public exploit | none known |
| Published | 2021-11-10 |
| Last modified | 2026-08-19 |
CISA KEV
| Name | Microsoft Exchange Server Remote Code Execution Vulnerability |
|---|---|
| Added | 2021-11-17 |
| Due | 2021-12-01 |
| Vendor / product | Microsoft / Exchange |
| Ransomware use | known |
Affected (1)
| Vendor | Product |
|---|---|
| microsoft | exchange server |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42321
- http://packetstormsecurity.com/files/166153/Microsoft-Exchange-Server-Remote-Code-Execution.html
- 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
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