CVE-2025-50864
📋 TL;DR
An origin validation error in the elysia-cors library allows attackers to bypass CORS restrictions by using malicious domains that contain legitimate domain names as substrings. This vulnerability affects any web application using elysia-cors version 1.3.0 or earlier for CORS validation, potentially exposing user data to unauthorized cross-origin access.
💻 Affected Systems
- elysia-cors
⚠️ 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
Attackers can bypass CORS policies entirely, enabling cross-origin attacks that steal sensitive user data, perform unauthorized actions, or conduct CSRF attacks against authenticated users.
Likely Case
Malicious websites can make unauthorized cross-origin requests to vulnerable applications, potentially accessing user data or performing actions on behalf of users.
If Mitigated
With proper server-side validation and additional security controls, the impact is limited to potential information disclosure from improperly configured endpoints.
🎯 Exploit Status
Exploitation requires crafting malicious domains that contain legitimate domain names as substrings (e.g., 'notexample.com' when 'example.com' is allowed).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.3.1 or later
Vendor Advisory: https://github.com/elysiajs/elysia-cors/commit/9b9eb92e32a7a4b43b6d5108668941701c33e221
Restart Required: No
Instructions:
1. Update elysia-cors to version 1.3.1 or later using npm: 'npm update elysia-cors' 2. Verify the update in package.json 3. Test CORS functionality after update
🔧 Temporary Workarounds
Implement custom origin validation
allOverride the default CORS origin validation with exact string matching
Implement custom origin validation middleware that performs exact domain matching instead of substring checking
🧯 If You Can't Patch
- Implement additional server-side validation for all sensitive endpoints
- Use Content Security Policy (CSP) headers to restrict cross-origin requests
🔍 How to Verify
Check if Vulnerable:
Check package.json for elysia-cors version <=1.3.0 or examine the origin validation logic in the CORS middlewareCheck Version:
npm list elysia-corsVerify Fix Applied:
Verify elysia-cors version is >=1.3.1 and test that domains like 'notexample.com' are rejected when 'example.com' is allowed📡 Detection & Monitoring
Log Indicators:
- Unusual cross-origin requests from domains containing legitimate domain names as substrings
- CORS policy violations from unexpected origins
Network Indicators:
- Cross-origin requests with suspicious origin headers
- Requests bypassing expected CORS restrictions
SIEM Query:
web.logs origin:*example.com* AND NOT origin:example.com🔗 References
- http://elysiajs.com
- https://github.com/elysiajs/elysia-cors/blob/main/src/index.ts
- https://github.com/elysiajs/elysia-cors/commit/9b9eb92e32a7a4b43b6d5108668941701c33e221
- https://github.com/elysiajs/elysia-cors/tree/main
- https://medium.com/@raghavagrawal_23036/cors-bypass-in-popular-opensource-library-ad27fb41e16a
