CVE-2025-53805
📋 TL;DR
This vulnerability allows an unauthorized attacker to trigger an out-of-bounds read in Windows Internet Information Services (IIS) through network access, causing a denial of service. It affects organizations running vulnerable versions of IIS on Windows servers. The attacker does not need authentication to exploit this vulnerability.
💻 Affected Systems
- Windows Internet Information Services (IIS)
📦 What is this software?
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 IIS web services, potentially affecting multiple websites and applications hosted on the server.
Likely Case
Temporary service interruption affecting specific IIS worker processes, requiring service restart to restore functionality.
If Mitigated
Limited impact with proper network segmentation and monitoring, allowing quick detection and response to service disruptions.
🎯 Exploit Status
The vulnerability description indicates network access without authentication is sufficient, suggesting relatively simple exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update Guide for specific patch versions
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-53805
Restart Required: Yes
Instructions:
1. Review Microsoft Security Update Guide for CVE-2025-53805. 2. Apply the latest Windows Server security updates. 3. Restart IIS services or the server as required by the update.
🔧 Temporary Workarounds
Network Access Restriction
windowsRestrict network access to IIS servers to only trusted sources using firewall rules.
New-NetFirewallRule -DisplayName "Restrict IIS Access" -Direction Inbound -Protocol TCP -LocalPort 80,443 -RemoteAddress TrustedIPRange -Action Allow
Application Request Routing Health Check
windowsImplement health checks and automatic failover for critical IIS applications.
🧯 If You Can't Patch
- Implement strict network segmentation and firewall rules to limit access to IIS servers
- Deploy web application firewalls (WAF) with DoS protection capabilities in front of IIS servers
🔍 How to Verify
Check if Vulnerable:
Check IIS version and compare against Microsoft's patched versions in the security advisory.Check Version:
Get-WindowsFeature -Name Web-Server | Select-Object Installed, VersionVerify Fix Applied:
Verify Windows Update history shows the relevant security update installed and IIS version matches patched versions.📡 Detection & Monitoring
Log Indicators:
- IIS worker process crashes (w3wp.exe)
- HTTP 503 Service Unavailable errors in IIS logs
- Event ID 1000 application crashes in Windows Event Log
Network Indicators:
- Unusual traffic patterns to IIS servers
- Multiple connection attempts from single sources
SIEM Query:
source="Windows Security" EventID=1000 ProcessName="w3wp.exe" OR source="IIS" status=503