CVE-2026-25577
📋 TL;DR
This vulnerability in the Emmett framework allows unauthenticated attackers to send malformed Cookie headers that trigger unhandled CookieError exceptions, causing HTTP 500 errors and denial of service. It affects all systems running Emmett versions prior to 1.3.11 that process HTTP requests with Cookie headers. The vulnerability requires no authentication and can be exploited remotely.
💻 Affected Systems
- Emmett Framework
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Sustained denial of service attacks could make web applications completely unavailable to legitimate users by exhausting server resources with repeated malformed requests.
Likely Case
Intermittent service disruption with HTTP 500 errors appearing in logs and occasional downtime for affected endpoints.
If Mitigated
Minimal impact with proper rate limiting and error handling in place, though some error logs would still be generated.
🎯 Exploit Status
Exploitation requires sending malformed Cookie headers, which is trivial to implement. No authentication or special privileges are needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.3.11
Vendor Advisory: https://github.com/emmett-framework/core/security/advisories/GHSA-x6cr-mq53-cc76
Restart Required: Yes
Instructions:
1. Update Emmett to version 1.3.11 or later using pip: 'pip install --upgrade emmett==1.3.11' 2. Restart your Emmett application 3. Verify the update was successful
🔧 Temporary Workarounds
Implement custom request middleware
allAdd middleware to validate and sanitize Cookie headers before they reach the vulnerable component
Implement custom request wrapper that catches CookieError exceptions
Web Application Firewall (WAF) rules
allConfigure WAF to block requests with malformed Cookie headers
Add WAF rule to validate Cookie header format
🧯 If You Can't Patch
- Implement rate limiting to prevent DoS attacks
- Deploy reverse proxy with request validation for Cookie headers
🔍 How to Verify
Check if Vulnerable:
Check if your Emmett version is below 1.3.11 and test by sending malformed Cookie headers to endpointsCheck Version:
python -c "import emmett; print(emmett.__version__)"Verify Fix Applied:
After updating to 1.3.11+, test that malformed Cookie headers no longer cause HTTP 500 errors📡 Detection & Monitoring
Log Indicators:
- Multiple HTTP 500 errors with CookieError exceptions in stack traces
- Unusual spikes in error responses
Network Indicators:
- Requests with malformed Cookie headers
- High volume of requests to same endpoints
SIEM Query:
source="web_logs" status=500 AND ("CookieError" OR "malformed cookie")