CVE-2026-30837
📋 TL;DR
CVE-2026-30837 is a Regular Expression Denial of Service (ReDoS) vulnerability in the Elysia TypeScript framework's URL validation. Attackers can cause significant performance degradation by sending specially crafted URLs that trigger inefficient regex processing. This affects any application using Elysia's t.String({ format: 'url' }) validation before version 1.4.26.
💻 Affected Systems
- Elysia TypeScript 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
Complete service unavailability due to CPU exhaustion, leading to denial of service for all users and potential cascading failures in dependent systems.
Likely Case
Significant performance degradation causing increased response times, timeouts, and partial service disruption for affected endpoints.
If Mitigated
Minimal impact with proper rate limiting, request validation, and monitoring in place to detect and block malicious patterns.
🎯 Exploit Status
Proof of concept available on GitHub demonstrates simple exploitation. Attack requires no authentication and minimal technical skill.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.4.26
Vendor Advisory: https://github.com/elysiajs/elysia/security/advisories/GHSA-f45g-68q3-5w8x
Restart Required: Yes
Instructions:
1. Update Elysia dependency to version 1.4.26 or later. 2. Run npm update elysia or yarn upgrade elysia. 3. Restart your application server. 4. Test URL validation functionality.
🔧 Temporary Workarounds
Custom URL Validation
allReplace vulnerable t.String({ format: 'url' }) with custom validation using a more efficient regex pattern or URL parsing library.
// Replace: t.String({ format: 'url' })
// With custom validation function
Rate Limiting
allImplement strict rate limiting on endpoints using URL validation to prevent repeated malicious requests.
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to block requests with suspicious URL patterns containing repeated protocol/hostname sequences.
- Deploy request monitoring and alerting for abnormal CPU usage patterns on endpoints using URL validation.
🔍 How to Verify
Check if Vulnerable:
Check package.json for Elysia version <1.4.26 and search codebase for t.String({ format: 'url' }) usage.Check Version:
npm list elysia | grep elysiaVerify Fix Applied:
After updating, verify Elysia version is ≥1.4.26 and test URL validation with the PoC patterns to ensure no performance degradation.📡 Detection & Monitoring
Log Indicators:
- Unusually long request processing times for URL validation endpoints
- CPU spikes correlated with specific URL patterns
- Increased error rates or timeouts on validation routes
Network Indicators:
- High volume of requests with similar URL structures containing repeated patterns
- Abnormal request patterns to validation endpoints
SIEM Query:
source="application_logs" AND (message="*t.String*url*" OR endpoint="*validate*") AND duration_ms > 5000