CVE-2025-53805 Overview
CVE-2025-53805 is an out-of-bounds read vulnerability in Windows Internet Information Services (IIS) that allows an unauthorized attacker to cause a denial of service condition over a network. This vulnerability affects multiple versions of Windows 11 and Windows Server, potentially impacting critical web infrastructure.
Critical Impact
Unauthenticated remote attackers can exploit this vulnerability to disrupt IIS web services, causing denial of service conditions that affect business-critical web applications and services.
Affected Products
- Microsoft Windows 11 22H2
- Microsoft Windows 11 23H2
- Microsoft Windows 11 24H2
- Microsoft Windows Server 2022
- Microsoft Windows Server 2022 23H2
- Microsoft Windows Server 2025
Discovery Timeline
- September 9, 2025 - CVE-2025-53805 published to NVD
- October 2, 2025 - Last updated in NVD database
Technical Details for CVE-2025-53805
Vulnerability Analysis
This vulnerability is classified as CWE-125 (Out-of-bounds Read), where Windows Internet Information Services improperly handles memory read operations. When processing certain network requests, IIS can be manipulated into reading memory beyond the intended buffer boundaries, leading to service disruption.
The out-of-bounds read condition occurs when IIS processes specially crafted network traffic. Unlike out-of-bounds write vulnerabilities that can lead to code execution, this read-based vulnerability primarily results in information disclosure or denial of service. In this case, the vulnerability triggers a denial of service condition, crashing or destabilizing the IIS worker process.
Root Cause
The root cause of CVE-2025-53805 lies in improper bounds checking within Windows Internet Information Services. When handling certain input data over the network, the affected component fails to properly validate buffer boundaries before performing read operations. This allows an attacker to craft requests that cause IIS to read beyond allocated memory regions, resulting in a crash or unresponsive state.
Attack Vector
The attack vector for this vulnerability is network-based, requiring no authentication or user interaction. An attacker can remotely send specially crafted requests to a vulnerable IIS server to trigger the out-of-bounds read condition. The attack does not require any privileges on the target system, making it particularly concerning for internet-facing IIS deployments.
The exploitation flow involves:
- The attacker identifies a target running a vulnerable version of Windows with IIS enabled
- The attacker crafts malicious network requests designed to trigger the out-of-bounds read
- Upon processing these requests, IIS reads memory beyond the intended buffer
- The out-of-bounds read causes the IIS worker process to crash or become unresponsive
- Service availability is impacted until the process recovers or is manually restarted
Detection Methods for CVE-2025-53805
Indicators of Compromise
- Unexpected IIS application pool crashes or restarts in Windows Event logs
- Unusual patterns of W3WP.exe process terminations
- Spike in HTTP 503 Service Unavailable responses from IIS servers
- Memory access violation errors in IIS-related Windows crash dumps
Detection Strategies
- Monitor Windows Application and System event logs for IIS worker process crashes with memory-related error codes
- Implement network intrusion detection rules to identify anomalous HTTP request patterns targeting IIS
- Deploy endpoint detection solutions like SentinelOne to detect exploitation attempts and abnormal IIS behavior
- Configure Web Application Firewall (WAF) rules to filter potentially malicious request patterns
Monitoring Recommendations
- Enable IIS Failed Request Tracing (FREB) to capture detailed information on requests preceding crashes
- Configure Windows Performance Monitor alerts for abnormal IIS worker process memory consumption
- Establish baseline metrics for IIS application pool health and alert on deviations
- Implement centralized logging for all IIS servers to correlate potential attack patterns across the environment
How to Mitigate CVE-2025-53805
Immediate Actions Required
- Apply the latest Microsoft security updates for affected Windows versions immediately
- Ensure IIS servers are behind properly configured network firewalls and WAFs
- Review and restrict network access to IIS servers, limiting exposure to trusted sources where possible
- Enable IIS application pool rapid-fail protection to automatically disable pools experiencing repeated crashes
Patch Information
Microsoft has released security updates to address this vulnerability. Detailed patch information and download links are available in the Microsoft Security Response Center (MSRC) Update Guide. Organizations should prioritize patching internet-facing IIS servers and apply updates through Windows Update, WSUS, or Microsoft Update Catalog.
Workarounds
- Implement network-level filtering using firewalls or load balancers to restrict access to IIS services from untrusted networks
- Configure rate limiting on IIS to help mitigate volumetric denial of service attempts
- Deploy a reverse proxy or CDN in front of IIS servers to provide an additional layer of protection
- If specific request patterns are identified as triggering the vulnerability, implement URL rewrite rules to block them
# Example: Enable IIS Application Pool Rapid-Fail Protection via PowerShell
Import-Module WebAdministration
Set-ItemProperty -Path "IIS:\AppPools\DefaultAppPool" -Name "failure.rapidFailProtection" -Value $true
Set-ItemProperty -Path "IIS:\AppPools\DefaultAppPool" -Name "failure.rapidFailProtectionInterval" -Value "00:05:00"
Set-ItemProperty -Path "IIS:\AppPools\DefaultAppPool" -Name "failure.rapidFailProtectionMaxCrashes" -Value 5
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
