CVE-2021-31209Microsoft Exchange Server Spoofing Vulnerability
- 6.5MediumCVSS base score
- 2.6%Exploitation in 30 daysEPSS · top 14% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Microsoft Exchange Server Spoofing Vulnerability
Timeline
ID reserved
By microsoft
- 27 days later
· 27 days later
Published
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoftCNA (assigner) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N/E:U/RL:O/RC:C |
| NVDNVD · Modified | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N |
- EPSS (exploitation in 30 days)
- 2.6% · top 14% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 9
- affected 15.02.0 – < 15.02.0858.012
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 20
- affected 15.01.0 – < 15.01.2242.010
Microsoft · Microsoft Exchange Server 2013 Cumulative Update 23
- affected 15.00.0 – < 15.00.1497.018
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 19
- affected 15.01.0 – < 15.01.2176.014
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 8
- affected 15.02.0 – < 15.02.0792.015
References
References2
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31209 (opens in a new tab)x_refsource_MISCx_transferred
- https://www.zerodayinitiative.com/advisories/ZDI-21-615/ (opens in a new tab)x_refsource_MISCx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-18122 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-31209)Record last updated .