CVE-2025-26682
📋 TL;DR
This CVE describes a resource exhaustion vulnerability in ASP.NET Core where an attacker can send specially crafted requests to consume excessive server resources without proper throttling. This allows denial of service attacks against affected web applications. Any ASP.NET Core application using vulnerable versions is affected.
💻 Affected Systems
- ASP.NET Core
📦 What is this software?
Asp.net Core by Microsoft
Asp.net Core by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability due to resource exhaustion, potentially affecting multiple applications on the same server.
Likely Case
Degraded performance and intermittent service disruptions under targeted attack.
If Mitigated
Minimal impact with proper rate limiting and resource monitoring in place.
🎯 Exploit Status
The vulnerability requires no authentication and can be exploited with simple HTTP requests.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Will be specified in Microsoft's security update
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-26682
Restart Required: Yes
Instructions:
1. Check Microsoft's security advisory for affected versions
2. Apply the latest security update for ASP.NET Core
3. Restart affected applications and services
4. Test application functionality post-update
🔧 Temporary Workarounds
Implement Rate Limiting
allConfigure ASP.NET Core rate limiting middleware to restrict request frequency per client
Add app.UseRateLimiter() in Program.cs with appropriate policies
Configure Request Limits
allSet maximum request size and timeout limits in Kestrel configuration
Configure in appsettings.json or Program.cs with Limits.MaxRequestBodySize, Limits.KeepAliveTimeout
🧯 If You Can't Patch
- Implement network-level rate limiting using WAF or load balancer
- Deploy additional monitoring for resource consumption anomalies
🔍 How to Verify
Check if Vulnerable:
Check ASP.NET Core version against Microsoft's advisory for affected versionsCheck Version:
dotnet --info | findstr "ASP.NET Core"Verify Fix Applied:
Verify ASP.NET Core version is updated to patched version and test with simulated attack patterns📡 Detection & Monitoring
Log Indicators:
- Sudden spikes in memory/CPU usage
- Increased error rates for 503/429 responses
- Unusual number of requests from single IPs
Network Indicators:
- High volume of similar requests to ASP.NET endpoints
- Abnormal request patterns bypassing normal user flows
SIEM Query:
source="iis" OR source="aspnet" (memory_usage > 90% OR cpu_usage > 90%) AND request_count > 1000