CVE-2021-40456
Windows AD FS Security Feature Bypass Vulnerability
Windows AD FS Security Feature Bypass Vulnerability
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Windows AD FS Security Feature Bypass Vulnerability
Windows AD FS Security Feature Bypass Vulnerability
- Record
CVE-2021-40456- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N/E:U/RL:O/RC:C - Weakness
- CWE-863
- Updated
- 2026-11-02
EUVDEUVD-2021-27633
Windows AD FS Security Feature Bypass Vulnerability
- Record
EUVD-2021-27633- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N/E:U/RL:O/RC:C - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-j5xg-6v4g-89vw
Windows AD FS Security Feature Bypass Vulnerability
Windows AD FS Security Feature Bypass Vulnerability
- Record
GHSA-j5xg-6v4g-89vw- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - Weakness
- CWE-863
- Updated
- 2026-11-02
NVD
Windows AD FS Security Feature Bypass Vulnerability
- Record
CVE-2021-40456- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:P/I:N/A:N - Weakness
- CWE-863
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-40456 is a medium vulnerability (CVSS 5.3) in Microsoft Windows Server 2019, published October 13, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.34%, the 83rd percentile. No source names a fixed version.