CVE-2025-55234
High CVSS 8.8Published 2025-09-09 · last changed 2026-06-17
The fix
Microsoft fixes this in updatesKB5065430, KB5065427, KB5065428, KB5065429, KB5065431, KB5065426, KB5065474, KB5065508, KB5065511, KB5065468, KB5065510, KB5065509, KB5065507, KB5065432, KB5065306, KB5065425. The fixed build differs per Windows version, so the row that matters is the one matching the machine you are looking at.
| Windows version | Fixed in build | Update | Released |
|---|---|---|---|
| Windows 10 for 32-bit Systems | 10.0.10240.21128 | KB5065430 | 2026-09-18 |
| Windows 10 for x64-based Systems | 10.0.10240.21128 | KB5065430 | 2026-09-18 |
| Windows 10 Version 1607 for 32-bit Systems | 10.0.14393.8422 | KB5065427 | 2026-09-18 |
| Windows 10 Version 1607 for x64-based Systems | 10.0.14393.8422 | KB5065427 | 2026-09-18 |
| Windows 10 Version 1809 for 32-bit Systems | 10.0.17763.7792 | KB5065428 | 2026-09-18 |
| Windows 10 Version 1809 for x64-based Systems | 10.0.17763.7792 | KB5065428 | 2026-09-18 |
| Windows 10 Version 21H2 for 32-bit Systems | 10.0.19044.6332 | KB5065429 | 2026-09-18 |
| Windows 10 Version 21H2 for ARM64-based Systems | 10.0.19044.6332 | KB5065429 | 2026-09-18 |
| Windows 10 Version 21H2 for x64-based Systems | 10.0.19044.6332 | KB5065429 | 2026-09-18 |
| Windows 10 Version 22H2 for 32-bit Systems | 10.0.19045.6332 | KB5065429 | 2026-09-18 |
| Windows 10 Version 22H2 for ARM64-based Systems | 10.0.19045.6332 | KB5065429 | 2026-09-18 |
| Windows 10 Version 22H2 for x64-based Systems | 10.0.19045.6332 | KB5065429 | 2026-09-18 |
| Windows 11 Version 22H2 for ARM64-based Systems | 10.0.22621.5909 | KB5065431 | 2026-09-18 |
| Windows 11 Version 22H2 for x64-based Systems | 10.0.22621.5909 | KB5065431 | 2026-09-18 |
| Windows 11 Version 23H2 for ARM64-based Systems | 10.0.22631.5909 | KB5065431 | 2026-09-18 |
| Windows 11 Version 23H2 for x64-based Systems | 10.0.22631.5909 | KB5065431 | 2026-09-18 |
| Windows 11 Version 24H2 for ARM64-based Systems | 10.0.26100.6584 | KB5065426, KB5065474 | 2026-09-18 |
| Windows 11 Version 24H2 for x64-based Systems | 10.0.26100.6584 | KB5065426, KB5065474 | 2026-09-18 |
| Windows Server 2008 for 32-bit Systems Service Pack 2 | 6.0.6003.23529 | KB5065508, KB5065511 | 2026-09-18 |
| Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) | 6.0.6003.23529 | KB5065508, KB5065511 | 2026-09-18 |
| Windows Server 2008 for x64-based Systems Service Pack 2 | 6.0.6003.23529 | KB5065508, KB5065511 | 2026-09-18 |
| Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) | 6.0.6003.23529 | KB5065508, KB5065511 | 2026-09-18 |
| Windows Server 2008 R2 for x64-based Systems Service Pack 1 | 6.1.7601.27929 | KB5065468, KB5065510 | 2026-09-18 |
| Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) | 6.1.7601.27929 | KB5065468, KB5065510 | 2026-09-18 |
| Windows Server 2012 | 6.2.9200.25675 | KB5065509 | 2026-09-18 |
| Windows Server 2012 R2 | 6.3.9600.22774 | KB5065507 | 2026-09-18 |
| Windows Server 2012 R2 (Server Core installation) | 6.3.9600.22774 | KB5065507 | 2026-09-18 |
| Windows Server 2012 (Server Core installation) | 6.2.9200.25675 | KB5065509 | 2026-09-18 |
| Windows Server 2016 | 10.0.14393.8422 | KB5065427 | 2026-09-18 |
| Windows Server 2016 (Server Core installation) | 10.0.14393.8422 | KB5065427 | 2026-09-18 |
| Windows Server 2019 | 10.0.17763.7792 | KB5065428 | 2026-09-18 |
| Windows Server 2019 (Server Core installation) | 10.0.17763.7792 | KB5065428 | 2026-09-18 |
| Windows Server 2022 | 10.0.20348.4171 | KB5065432, KB5065306 | 2026-09-18 |
| Windows Server 2022, 23H2 Edition (Server Core installation) | 10.0.25398.1849 | KB5065425 | 2026-09-18 |
| Windows Server 2022 (Server Core installation) | 10.0.20348.4171 | KB5065432, KB5065306 | 2026-09-18 |
| Windows Server 2025 | 10.0.26100.6584 | KB5065426, KB5065474 | 2026-09-18 |
| Windows Server 2025 (Server Core installation) | 10.0.26100.6584 | KB5065426, KB5065474 | 2026-09-18 |
Having the KB is not the same as knowing whether a machine has it. Windows updates supersede each other, so the update you installed often covers a fix that shipped in an earlier one. Paste your build into the patch checker and it walks that chain for you.
What it is
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.
Sources
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H