CVE-2021-31209 json
Microsoft Exchange Server Spoofing Vulnerability
published 2021-05-11 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-18122
- cvss
- 8.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 2.6%
- EPSS 2.6% chance of exploitation in 30 days, percentile 85%
- public exploits
- 0
- none known
Summary
Microsoft Exchange Server Spoofing Vulnerability
Patch / fix
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 9 15.02.0858.012
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 20 15.01.2242.010
- Microsoft Microsoft Exchange Server 2013 Cumulative Update 23 15.00.1497.018
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 19 15.01.2176.014
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 8 15.02.0792.015
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 20 mo ago
Exploit prediction
2.63% chance of exploitation in the next 30 days, higher than 85% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.5 | 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 |
| CNA | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N |
| CNA | 3.1 | 8.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N |
| NVD | 2.0 | 5.8 | AV:N/AC:M/Au:N/C:P/I:P/A:N |
Affected products
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 9
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 20
- Microsoft Microsoft Exchange Server 2013 Cumulative Update 23
- Microsoft Microsoft Exchange Server 2016 Cumulative Update 19
- Microsoft Microsoft Exchange Server 2019 Cumulative Update 8
Classification
- Weakness
-
- CWE-290 Authentication Bypass by Spoofing
- Technology feeds
References
-
portal.msrc.microsoft.com
/en-US/security-guidance/advisory/CVE-2021-31209
patch, vendor-advisory
-
zerodayinitiative.com
/advisories/ZDI-21-615/
third-party-advisory, vdb-entry
Sources
- CVE List CVE-2021-31209
- NVD CVE-2021-31209
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.