CVE-2025-54918: Windows 10 Privilege Escalation Flaw

CVE-2025-54918 Overview

CVE-2025-54918 is an improper authentication vulnerability in Microsoft Windows NTLM that allows an authorized attacker to elevate privileges over a network. This flaw affects the NTLM authentication protocol, a critical component used for network authentication across Windows environments. An attacker with low-privilege network access can exploit this vulnerability to gain elevated privileges, potentially compromising domain controllers, file servers, and other critical infrastructure.

Critical Impact

Authenticated attackers can leverage this NTLM authentication flaw to escalate privileges across the network, potentially achieving domain-level access and compromising enterprise Windows environments.

Affected Products

• Microsoft Windows 10 (versions 1507, 1607, 1809, 21H2, 22H2)
• Microsoft Windows 11 (versions 22H2, 23H2, 24H2)
• Microsoft Windows Server 2008 SP2, 2008 R2 SP1, 2012, 2012 R2, 2016, 2019, 2022, 2022 23H2, 2025

Discovery Timeline

• September 9, 2025 - CVE-2025-54918 published to NVD
• October 2, 2025 - Last updated in NVD database

Technical Details for CVE-2025-54918

Vulnerability Analysis

This vulnerability stems from improper authentication handling within the Windows NTLM protocol implementation. NTLM (NT LAN Manager) is a legacy authentication protocol that remains widely deployed in Windows environments for backward compatibility and specific use cases. The flaw allows an attacker who already has low-level authenticated access to the network to bypass proper privilege verification mechanisms.

The vulnerability is classified under CWE-287 (Improper Authentication), indicating that the NTLM protocol fails to properly verify the identity or privileges of a user during certain authentication exchanges. This can be exploited remotely over the network without requiring user interaction, making it particularly dangerous in enterprise environments where NTLM is commonly used for internal authentication.

Root Cause

The root cause of CVE-2025-54918 lies in the improper validation of authentication credentials within the NTLM protocol stack. During specific authentication sequences, the protocol fails to adequately verify that the requesting entity possesses the appropriate privileges for the requested operation. This authentication bypass allows attackers to present manipulated or replayed credentials that are incorrectly accepted as valid for higher-privilege operations.

The vulnerability affects the core Windows authentication subsystem, which explains the extensive list of affected products spanning from legacy Windows Server 2008 to the latest Windows Server 2025 and Windows 11 24H2 releases.

Attack Vector

The attack vector for CVE-2025-54918 is network-based, requiring the attacker to have initial low-privilege authenticated access to the target network. The exploitation flow typically involves:

1. The attacker establishes an authenticated session using valid low-privilege credentials
2. The attacker crafts specially designed NTLM authentication requests that exploit the improper authentication validation
3. The vulnerable NTLM implementation incorrectly grants elevated privileges to the attacker
4. With escalated privileges, the attacker can access protected resources, execute commands with higher permissions, or pivot to other systems

This vulnerability is particularly concerning in Active Directory environments where NTLM relay attacks and authentication manipulation can lead to rapid lateral movement and domain compromise. The attack does not require user interaction and has low complexity, making it an attractive target for threat actors.

Detection Methods for CVE-2025-54918

Indicators of Compromise

• Unusual NTLM authentication patterns including authentication attempts from unexpected source systems or service accounts
• Anomalous privilege elevation events in Windows Security Event Logs (Event IDs 4672, 4624 with elevated token types)
• Unexpected network traffic on ports commonly associated with NTLM authentication (TCP 445, 139, 135)
• Signs of credential relay activity between systems that do not typically communicate

Detection Strategies

• Monitor Windows Security Event Logs for Event ID 4776 (NTLM credential validation) with unusual patterns or failure codes
• Deploy network detection rules to identify abnormal NTLM authentication traffic and potential relay attempts
• Enable Extended Protection for Authentication (EPA) audit logging to detect authentication bypass attempts
• Utilize SentinelOne Singularity platform for behavioral detection of privilege escalation activities following NTLM authentication

Monitoring Recommendations

• Configure Windows Advanced Audit Policy to capture detailed NTLM authentication events
• Implement SIEM correlation rules to detect rapid privilege changes following network authentication
• Monitor for processes spawned with elevated privileges immediately after NTLM authentication sequences
• Track lateral movement patterns that may indicate exploitation of this vulnerability for network propagation

How to Mitigate CVE-2025-54918

Immediate Actions Required

• Apply the latest Microsoft security updates from the September 2025 Patch Tuesday release
• Audit NTLM usage across the environment and identify systems that can be migrated to Kerberos authentication
• Enable SMB signing and LDAP signing to reduce the risk of NTLM relay attacks
• Implement network segmentation to limit the blast radius of potential privilege escalation attacks

Patch Information

Microsoft has released security updates addressing CVE-2025-54918 through their standard security update channels. Organizations should consult the Microsoft Security Response Center advisory for specific patch details and affected build numbers. The updates are available through Windows Update, Microsoft Update Catalog, and WSUS for enterprise deployments.

Priority should be given to patching domain controllers, authentication servers, and systems exposed to potentially compromised network segments.

Workarounds

• Disable NTLM authentication where possible by configuring Group Policy settings under Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options > Network Security: Restrict NTLM
• Enable Extended Protection for Authentication (EPA) to add channel binding tokens to NTLM authentication
• Implement the principle of least privilege to minimize the impact of successful privilege escalation
• Consider deploying Protected Users security group for high-value accounts to prevent NTLM authentication entirely for those identities

# Group Policy configuration to restrict NTLM usage
# Path: Computer Configuration > Windows Settings > Security Settings > 
#       Local Policies > Security Options

# To audit NTLM usage before blocking:
# "Network Security: Restrict NTLM: Audit NTLM authentication in this domain" = Enable all

# To restrict NTLM after audit:
# "Network Security: Restrict NTLM: NTLM authentication in this domain" = Deny all accounts