CVE-2021-26858
Microsoft Exchange Server Remote Code Execution Vulnerability
IN CISA KEV
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
- Vendor
- Microsoft
- Product
- Exchange Server
- CVSS
- No score recorded (no NVD record loaded for this entry)
- CWE
- Not recorded
- Published
- Not recorded
- NVD modified
- Not recorded
CISA KEV
- Date added
- 2021-11-03
- Due date
- 2022-05-03
- Ransomware use
- Known
- Required action
- Apply updates per vendor instructions.
EPSS
93.7% chance of exploitation in the next 30 days (percentile 99th)
FIRST EPSS, updated 17 Oct 2026. About EPSS
CVSS is severity, EPSS is likelihood, KEV means already exploited. EPSS is a statistical probability, not a certainty: a low score does not make a bug safe, and a high one does not prove it is being exploited.
Data last updated 18 Oct 2026. Sources: NVD API 2.0, CISA KEV catalog, FIRST EPSS. Links: NVD, CISA KEV. Metadata only. ThreatWire does not host exploit code.