CVE-2025-13953
📋 TL;DR
This vulnerability allows attackers to bypass authentication in the GTT Tax Information System by impersonating the local WebSocket connection used for Active Directory/LDAP login. Attackers with local machine or internal network access can authenticate as any domain user without valid credentials. This affects organizations using the vulnerable GTT Tax Information System application.
💻 Affected Systems
- GTT Tax Information System
⚠️ 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 compromise of the tax information system allowing attackers to authenticate as any user, access sensitive taxpayer data, modify tax records, and disrupt government operations.
Likely Case
Unauthorized access to tax information system by internal or compromised users, leading to data theft, privilege escalation, and potential manipulation of tax records.
If Mitigated
Limited impact with proper network segmentation, monitoring, and authentication controls in place, though risk remains for authorized users with malicious intent.
🎯 Exploit Status
Exploitation requires access to local machine or internal network to impersonate WebSocket. Attackers need understanding of the application's WebSocket authentication flow.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified
Vendor Advisory: https://www.incibe.es/en/incibe-cert/notices/aviso/bypass-authentication-method-gtt-sistema-de-informacion-tributario
Restart Required: No
Instructions:
No official patch available. Contact GTT vendor for updated version with proper WebSocket authentication validation.
🔧 Temporary Workarounds
Network Segmentation
allRestrict access to the WebSocket endpoint to only trusted systems and implement strict network controls.
WebSocket Authentication Validation
allImplement proper origin validation and authentication checks for WebSocket connections.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the GTT system from untrusted networks
- Deploy additional authentication layers (MFA) and monitor for unusual authentication patterns
🔍 How to Verify
Check if Vulnerable:
Test if WebSocket authentication accepts connections from unauthorized origins or if authentication can be bypassed by impersonating the WebSocket.Check Version:
Check application version through administrative interface or contact vendor for version information.Verify Fix Applied:
Verify that WebSocket connections now properly validate origin and authentication tokens, and cannot be impersonated.📡 Detection & Monitoring
Log Indicators:
- Unusual WebSocket connection patterns
- Authentication attempts from unexpected IPs or systems
- Multiple failed followed by successful authentication from same source
Network Indicators:
- WebSocket traffic from unauthorized sources
- Unusual authentication patterns in network traffic
SIEM Query:
source="gtt_websocket" AND (event_type="authentication" AND result="success") FROM unusual_ip_list