Executive brief
A vulnerability in the Windows SMB client, which handles file and printer sharing, could allow an attacker to gain elevated permissions on a target system. By tricking a computer into connecting to a malicious server, an attacker can capture authentication details and escalate their access. This flaw is reportedly being exploited in the wild, posing a significant risk to corporate network security and data integrity.
Technical details
An improper access control vulnerability (CWE-284) exists in the Microsoft Windows SMB Client. An authenticated attacker with low privileges can execute a malicious script to coerce a victim machine into connecting back to an attacker-controlled system via the SMB protocol. During this connection, the victim machine attempts to authenticate, allowing the attacker to capture or relay authentication credentials to escalate privileges. This vulnerability is reachable over the network and has been added to CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation. Patches are available from Microsoft for various versions of Windows and Windows Server.
Affected products
- Microsoft Windows Windows 10, Windows 11, Windows Server 2008, 2012, 2016, 2019, 2022, 2025
Timeline
- 2025-06-10: other: CVE received by Microsoft
- 2025-07-10: other: Initial analysis by NIST
- 2025-10-20: advisory: Vulnerability published by Microsoft
- 2025-10-20: kev added: Added to CISA KEV catalog due to active exploitation