cbcvebase.
CVE-2025-55234
published 2025-09-09

CVE-2025-55234: SMB Server might be susceptible to relay attacks depending on the configuration. An attacker who successfully exploited these vulnerabilities could perform…

PriorityP274critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
18.83%
97.0th percentile
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

47 ranges· showing 25
VendorProductVersion rangeFixed in
microsoftwindows_10_1507< 10.0.10240.2112810.0.10240.21128
microsoftwindows_10_1607< 10.0.14393.842210.0.14393.8422
microsoftwindows_10_1809< 10.0.17763.779210.0.17763.7792
microsoftwindows_10_21h2< 10.0.19044.633210.0.19044.6332
microsoftwindows_10_22h2< 10.0.19045.633210.0.19045.6332
microsoftwindows_10_version_1507>= 10.0.10240.0 < 10.0.10240.2112810.0.10240.21128
microsoftwindows_10_version_1607>= 10.0.14393.0 < 10.0.14393.842210.0.14393.8422
microsoftwindows_10_version_1809>= 10.0.17763.0 < 10.0.17763.779210.0.17763.7792
microsoftwindows_10_version_21h2>= 10.0.19044.0 < 10.0.19044.633210.0.19044.6332
microsoftwindows_10_version_22h2>= 10.0.19045.0 < 10.0.19045.633210.0.19045.6332
microsoftwindows_11_22h2< 10.0.22621.590910.0.22621.5909
microsoftwindows_11_23h2< 10.0.22631.590910.0.22631.5909
microsoftwindows_11_24h2< 10.0.26100.650810.0.26100.6508
microsoftwindows_11_version_22h2>= 10.0.22621.0 < 10.0.22621.590910.0.22621.5909
microsoftwindows_11_version_22h3>= 10.0.22631.0 < 10.0.22631.590910.0.22631.5909
microsoftwindows_11_version_23h2>= 10.0.22631.0 < 10.0.22631.590910.0.22631.5909
microsoftwindows_11_version_24h2>= 10.0.26100.0 < 10.0.26100.658410.0.26100.6584
microsoftwindows_server_2008
microsoftwindows_server_2008_r2_service_pack_1>= 6.1.7601.0 < 6.1.7601.279296.1.7601.27929
microsoftwindows_server_2008_service_pack_2>= 6.0.6003.0 < 6.0.6003.235296.0.6003.23529
microsoftwindows_server_2012
microsoftwindows_server_2012>= 6.2.9200.0 < 6.2.9200.256756.2.9200.25675
microsoftwindows_server_2012_r2>= 6.3.9600.0 < 6.3.9600.227746.3.9600.22774
microsoftwindows_server_2016< 10.0.14393.842210.0.14393.8422
microsoftwindows_server_2016>= 10.0.14393.0 < 10.0.14393.842210.0.14393.8422

Detection & IOCsextracted from sources · hover to see the quote

  • Enable and monitor SMB Server signing audit events to detect clients connecting without signing, which may indicate relay attack exposure or incompatible clients.
  • Monitor for SMB relay attack patterns (NTLM relay) targeting SMB Server endpoints where signing and EPA are not enforced; successful exploitation grants the privileges of the compromised user.
  • Use the September 9, 2025 security update audit capabilities (KB5066913 guidance) to identify SMB clients not supporting signing or EPA before enforcing hardening, as exploitation is rated 'More Likely' and the vulnerability is publicly disclosed.
  • ·SMB Server Extended Protection for Authentication (EPA) is a supported hardening mechanism but must be explicitly adopted; absence of EPA leaves the server vulnerable to relay attacks.
  • ·The September 9, 2025 security updates add audit-only capabilities; actual protection requires separately adopting SMB Server signing and EPA hardening measures.

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vendor_msrc8.8HIGH
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