CVE-2025-33056
📋 TL;DR
This vulnerability in Microsoft's Local Security Authority Server allows unauthorized attackers to cause denial of service over a network. It affects Windows systems running vulnerable versions of the Local Security Authority Subsystem Service. Attackers can disrupt authentication and security operations on affected systems.
💻 Affected Systems
- Microsoft Windows
📦 What is this software?
Windows 10 1507 by Microsoft
Windows 10 1507 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1607 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 1809 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete disruption of authentication services, preventing users from logging in or accessing resources, potentially leading to extended system downtime.
Likely Case
Temporary service disruption affecting authentication and security policy enforcement, requiring system restart to restore functionality.
If Mitigated
Minimal impact with proper network segmentation and access controls limiting exposure to trusted networks only.
🎯 Exploit Status
Network-based attack requiring no authentication. Complexity is low as it targets a core Windows service.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update for specific KB number
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-33056
Restart Required: Yes
Instructions:
1. Open Windows Update settings
2. Check for updates
3. Install all security updates
4. Restart system when prompted
🔧 Temporary Workarounds
Network Segmentation
windowsRestrict network access to LSASRV service ports (typically 445/TCP, 139/TCP) to trusted hosts only
Use Windows Firewall: New-NetFirewallRule -DisplayName 'Block LSASRV' -Direction Inbound -Protocol TCP -LocalPort 445,139 -Action Block
Service Hardening
windowsApply additional security controls to LSASS process
AuditPol /set /subcategory:'Process Creation' /success:enable /failure:enable
🧯 If You Can't Patch
- Implement strict network segmentation to isolate affected systems from untrusted networks
- Deploy additional monitoring and alerting for LSASS process crashes or authentication failures
🔍 How to Verify
Check if Vulnerable:
Check Windows version and compare against Microsoft's security bulletin for affected versionsCheck Version:
wmic os get caption,version,buildnumberVerify Fix Applied:
Verify Windows Update history shows the relevant security patch installed and system has been restarted📡 Detection & Monitoring
Log Indicators:
- Event ID 1000 from lsass.exe crashes in Application logs
- Authentication failures in Security logs following service disruption
Network Indicators:
- Unusual traffic to port 445/TCP from unauthorized sources
- Multiple connection attempts to LSASRV endpoints
SIEM Query:
source='windows' AND (event_id=1000 AND process_name='lsass.exe') OR (event_id=4625 AND failure_reason='Unknown user name or bad password')