CVE-2025-21285
📋 TL;DR
This vulnerability in Microsoft Message Queuing (MSMQ) allows attackers to cause a denial of service condition by sending specially crafted packets to vulnerable systems. It affects Windows systems with MSMQ enabled, potentially causing service disruption. The vulnerability stems from improper handling of NULL pointer dereferences in MSMQ components.
💻 Affected Systems
- Microsoft Message Queuing (MSMQ)
📦 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 service disruption of MSMQ functionality, potentially affecting dependent applications and business processes that rely on message queuing.
Likely Case
MSMQ service crashes or becomes unresponsive, requiring service restart and causing temporary disruption to message processing.
If Mitigated
Minimal impact with proper network segmentation and access controls limiting exposure to trusted sources only.
🎯 Exploit Status
Attackers can trigger the vulnerability by sending specially crafted packets to the MSMQ service without authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Latest security updates from Microsoft (specific KB numbers vary by OS version)
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21285
Restart Required: Yes
Instructions:
1. Apply the latest Windows security updates from Microsoft. 2. Restart affected systems to complete the patch installation. 3. Verify MSMQ service is running properly after restart.
🔧 Temporary Workarounds
Disable MSMQ Service
WindowsStop and disable the MSMQ service if not required for business operations
Stop-Service -Name MSMQ
Set-Service -Name MSMQ -StartupType Disabled
Block MSMQ Ports
WindowsBlock network access to MSMQ ports (TCP 1801, TCP 2103, TCP 2105, UDP 3527, UDP 1801)
New-NetFirewallRule -DisplayName "Block MSMQ" -Direction Inbound -Protocol TCP -LocalPort 1801,2103,2105 -Action Block
New-NetFirewallRule -DisplayName "Block MSMQ UDP" -Direction Inbound -Protocol UDP -LocalPort 3527,1801 -Action Block
🧯 If You Can't Patch
- Implement strict network segmentation to isolate MSMQ servers from untrusted networks
- Monitor MSMQ service health and implement automated restart procedures for service crashes
🔍 How to Verify
Check if Vulnerable:
Check if MSMQ service is installed and running: Get-Service MSMQ | Select-Object Status, StartTypeCheck Version:
Get-WmiObject Win32_Service | Where-Object {$_.Name -eq 'MSMQ'} | Select-Object Name, State, StartModeVerify Fix Applied:
Verify Windows Update history contains the relevant security update and MSMQ service version📡 Detection & Monitoring
Log Indicators:
- MSMQ service crash events in Windows System logs (Event ID 7031, 7034)
- Unexpected MSMQ service restarts
- Application errors related to MSMQ connectivity
Network Indicators:
- Unusual traffic patterns to MSMQ ports (1801, 2103, 2105, 3527)
- Multiple connection attempts to MSMQ from single sources
SIEM Query:
EventID=7031 OR EventID=7034 AND ServiceName="MSMQ" | stats count by SourceIP, ServiceName