CVE-2025-55234

EUVD-2025-27294

09.09.2025, 17:16

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.

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
NIST	Primary	8.8 HIGH	NETWORK	LOW	NONE	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
microsoft	CNA	8.8 HIGH				CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Base Score

CVSS 3.x

EPSS Score

Percentile: 52%

Affected Products (NVD)

Vendor	Product	Version
microsoft	windows_10_1507	𝑥 < 10.0.10240.21128
microsoft	windows_10_1507	𝑥 < 10.0.10240.21128
microsoft	windows_10_1607	𝑥 < 10.0.14393.8422
microsoft	windows_10_1607	𝑥 < 10.0.14393.8422
microsoft	windows_10_1809	𝑥 < 10.0.17763.7792
microsoft	windows_10_1809	𝑥 < 10.0.17763.7792
microsoft	windows_10_21h2	𝑥 < 10.0.19044.6332
microsoft	windows_10_22h2	𝑥 < 10.0.19045.6332
microsoft	windows_11_22h2	𝑥 < 10.0.22621.5909
microsoft	windows_11_23h2	𝑥 < 10.0.22631.5909
microsoft	windows_11_24h2	𝑥 < 10.0.26100.6508
microsoft	windows_server_2008	-
microsoft	windows_server_2008	-
microsoft	windows_server_2012	-
microsoft	windows_server_2016	𝑥 < 10.0.14393.8422
microsoft	windows_server_2019	𝑥 < 10.0.17763.7792
microsoft	windows_server_2022	𝑥 < 10.0.20348.4106
microsoft	windows_server_2022_23h2	𝑥 < 10.0.25398.1849
microsoft	windows_server_2025	𝑥 < 10.0.26100.6508

𝑥

= Vulnerable software versions

Windows Releases

Platform

Version

Windows 10

(x64, x86)	KB5065430
1607 (x64, x86)	KB5065427
1809 (x64, x86)	KB5065428
21H2 (arm64, x64, x86)	KB5065429
22H2 (arm64, x64, x86)	KB5065429

Windows 11

22H2 (arm64, x64)	KB5065431
23H2 (arm64, x64)	KB5065431
24H2 (arm64, x64)	KB5065426

Windows Server 2008

Service Pack 2 (x64, x86)	KB5065511
Service Pack 2 Server Core (x64, x86)	KB5065511

Windows Server 2008 R2

Service Pack 1 (x64)	KB5065510
Service Pack 1 Server Core (x64)	KB5065510

Windows Server 2012

Server Core	KB5065509
Standard	KB5065509

Windows Server 2012 R2

Server Core	KB5065507
Standard	KB5065507

Windows Server 2016

Server Core	KB5065427
Standard	KB5065427

Windows Server 2019

Server Core	KB5065428
Standard	KB5065428

Windows Server 2022

23H2 Server Core	KB5065425
Server Core	KB5065306
Standard	KB5065306

Windows Server 2025

Server Core	KB5065426
Standard	KB5065426

Common Weakness Enumeration

CWE-287 - Improper Authentication
When an actor claims to have a given identity, the software does not prove or insufficiently proves that the claim is correct.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-55234

https://www.vicarius.io/vsociety/posts/cve-2025-55234-detection-script-smb-server-vulnerability-affecting-microsoft-systems

https://www.vicarius.io/vsociety/posts/cve-2025-55234-mitigation-script-smb-server-vulnerability-affecting-microsoft-systems