6.5

CVE-2021-31209: microsoft exchange_server Authentication Bypass by Spoofing

CVSS: 6.5v3.1MediumModified
Published 11-05-2021Last modified 28-02-2025
Open JSON

Vulnerability summary

CVE-2021-31209 is a medium (CVSS 6.5) Authentication Bypass by Spoofing vulnerability in microsoft exchange_server. EPSS estimates a 2.63% chance of exploitation in the next 30 days, higher than 85.2% of scored vulnerabilities.

Overall risk
27/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
2.63%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 11-05-2021
    PublishedVulnerability first disclosed.
  2. 28-02-2025
    Last modifiedVulnerability information updated.

Description

Microsoft Exchange Server Spoofing Vulnerability

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

2.63%

Chance of exploitation in the next 30 days

Percentile

85%

Versus all other CVEs

30-day change

0.00 pp

From 2.63% on 20-09-2026

20-09-202620-10-2026
EPSS score
2.63%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Microsoft6 products

1 vendor · 6 products

References

2 links