CVE-2025-55234: Microsoft Windows 10 1507

Critical severity, CVSS 9.8. EPSS: 20.1% chance of exploitation in the next 30 days.

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.

Affected products

• Microsoft Windows 10 1507: before 10.0.10240.21128 (fixed in 10.0.10240.21128)
• Microsoft Windows 10 1607: before 10.0.14393.8422 (fixed in 10.0.14393.8422)
• Microsoft Windows 10 1809: before 10.0.17763.7792 (fixed in 10.0.17763.7792)
• Microsoft Windows 10 21h2: before 10.0.19044.6332 (fixed in 10.0.19044.6332)
• Microsoft Windows 10 22h2: before 10.0.19045.6332 (fixed in 10.0.19045.6332)
• Microsoft Windows 11 22h2: before 10.0.22621.5909 (fixed in 10.0.22621.5909)
• Microsoft Windows 11 23h2: before 10.0.22631.5909 (fixed in 10.0.22631.5909)
• Microsoft Windows 11 24h2: before 10.0.26100.6508 (fixed in 10.0.26100.6508)
• Microsoft Windows Server 2008: affected versions not specified; version r2 only
• Microsoft Windows Server 2012: affected versions not specified; version r2 only
• Microsoft Windows Server 2016: before 10.0.14393.8422 (fixed in 10.0.14393.8422)
• Microsoft Windows Server 2019: before 10.0.17763.7792 (fixed in 10.0.17763.7792)
• Microsoft Windows Server 2022: before 10.0.20348.4106 (fixed in 10.0.20348.4106)
• Microsoft Windows Server 2022 23h2: before 10.0.25398.1849 (fixed in 10.0.25398.1849)
• Microsoft Windows Server 2025: before 10.0.26100.6508 (fixed in 10.0.26100.6508)

Published 2025-09-09. Last modified 2026-06-17.