Windows 10 Version 1507: Improper Authentication
CVE-2025-55234 is a critical-severity improper authentication vulnerability in Windows 10 Version 1507 from Microsoft, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 10.0.10240.21128 as the first without the flaw, so updating Windows 10 Version 1507 to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 20.8% chance of exploitation within 30 days, which is in the top 2.41% of all scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Windows 10 Version 1507 to 10.0.10240.21128 or a later version.
- Update Windows 10 Version 1607 to 10.0.14393.8422 or a later version.
- Update Windows 10 Version 1809 to 10.0.17763.7792 or a later version.
- Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows 10 Version 1507 | 10.0.10240.0 up to, but not including, 10.0.10240.21128 | 10.0.10240.21128 |
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 up to, but not including, 10.0.14393.8422 | 10.0.14393.8422 |
| Microsoft | Windows 10 Version 1809 | 10.0.17763.0 up to, but not including, 10.0.17763.7792 | 10.0.17763.7792 |
| Microsoft | Windows 10 Version 21H2 | 10.0.19044.0 up to, but not including, 10.0.19044.6332 | 10.0.19044.6332 |
| Microsoft | Windows 10 Version 22H2 | 10.0.19045.0 up to, but not including, 10.0.19045.6332 | 10.0.19045.6332 |
| Microsoft | Windows 11 version 22H2 | 10.0.22621.0 up to, but not including, 10.0.22621.5909 | 10.0.22621.5909 |
| Microsoft | Windows 11 version 22H3 | 10.0.22631.0 up to, but not including, 10.0.22631.5909 | 10.0.22631.5909 |
| Microsoft | Windows 11 Version 23H2 | 10.0.22631.0 up to, but not including, 10.0.22631.5909 | 10.0.22631.5909 |
| Microsoft | Windows 11 Version 24H2 | 10.0.26100.0 up to, but not including, 10.0.26100.6584 | 10.0.26100.6584 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 | 6.1.7601.0 up to, but not including, 6.1.7601.27929 | 6.1.7601.27929 |
| Microsoft | Windows Server 2008 R2 Service Pack 1 (Server Core installation) | 6.1.7601.0 up to, but not including, 6.1.7601.27929 | 6.1.7601.27929 |
| Microsoft | Windows Server 2008 Service Pack 2 | 6.0.6003.0 up to, but not including, 6.0.6003.23529 | 6.0.6003.23529 |
| Microsoft | Windows Server 2008 Service Pack 2 (Server Core installation) | 6.0.6003.0 up to, but not including, 6.0.6003.23529 | 6.0.6003.23529 |
| Microsoft | Windows Server 2012 | 6.2.9200.0 up to, but not including, 6.2.9200.25675 | 6.2.9200.25675 |
| Microsoft | Windows Server 2012 (Server Core installation) | 6.2.9200.0 up to, but not including, 6.2.9200.25675 | 6.2.9200.25675 |
| Microsoft | Windows Server 2012 R2 | 6.3.9600.0 up to, but not including, 6.3.9600.22774 | 6.3.9600.22774 |
| Microsoft | Windows Server 2012 R2 (Server Core installation) | 6.3.9600.0 up to, but not including, 6.3.9600.22774 | 6.3.9600.22774 |
| Microsoft | Windows Server 2016 | 10.0.14393.0 up to, but not including, 10.0.14393.8422 | 10.0.14393.8422 |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.14393.0 up to, but not including, 10.0.14393.8422 | 10.0.14393.8422 |
| Microsoft | Windows Server 2019 | 10.0.17763.0 up to, but not including, 10.0.17763.7792 | 10.0.17763.7792 |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.17763.0 up to, but not including, 10.0.17763.7792 | 10.0.17763.7792 |
| Microsoft | Windows Server 2022 | 10.0.20348.0 up to, but not including, 10.0.20348.4171 | 10.0.20348.4171 |
| Microsoft | Windows Server 2022, 23H2 Edition (Server Core installation) | 10.0.25398.0 up to, but not including, 10.0.25398.1849 | 10.0.25398.1849 |
| Microsoft | Windows Server 2025 | 10.0.26100.0 up to, but not including, 10.0.26100.6584 | 10.0.26100.6584 |
| Microsoft | Windows Server 2025 (Server Core installation) | 10.0.26100.0 up to, but not including, 10.0.26100.6584 | 10.0.26100.6584 |
Version data comes from the organisation that assigned the CVE; 10 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | CNA (microsoft.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
SMB Server might be susceptible to relay attacks depending on the configuration. An attacker who successfully exploited these vulnerabilities could perform relay attacks and make the users subject to elevation of privilege attacks. The SMB Server already supports mechanisms for hardening against relay attacks: SMB Server signing SMB Server Extended Protection for Authentication (EPA) Microsoft is releasing this CVE to provide customers with audit capabilities to help them to assess their environment and to identify any potential device or software incompatibility issues before deploying SMB Server hardening measures that protect against relay attacks. If you have not already enabled SMB Server hardening measures, we advise customers to take the following actions to be protected from these relay attacks: Assess your environment by utilizing the audit capabilities that we are exposing in the September 2025 security updates. See Support for Audit Events to deploy SMB Server Hardening—SMB Server Signing & SMB Server EPA. Adopt appropriate SMB Server hardening measures.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Authentication
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
How developers prevent this class of flaw
- Use an authentication framework or library such as the OWASP ESAPI Authentication feature.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Windows 10 Version 1507
- 7.0 High severity
- 7.8 High severity
- 7.0 High severity
- 7.7 High severity
- 7.0 High severity
Recent Improper Authentication vulnerabilities
- 8.8 High severity
- 9.8 Critical severity
- 9.1 Critical severity
- 8.8 High severity
- 9.4 Critical severity
- 7.3 High severity
Spotted an error? Tell us.