CVE-2026-3873
📋 TL;DR
CVE-2026-3873 is a hard-coded credentials vulnerability in Avantra that allows attackers to bypass authentication and access functionality not properly restricted by access control lists. This affects all Avantra installations before version 25.3.0, potentially exposing sensitive system operations and data.
💻 Affected Systems
- Avantra
⚠️ 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 system compromise allowing unauthorized users to execute administrative functions, modify configurations, access sensitive data, and potentially pivot to other systems in the environment.
Likely Case
Unauthorized access to administrative interfaces leading to configuration changes, data exfiltration, and disruption of monitoring/management operations.
If Mitigated
Limited impact with proper network segmentation and additional authentication layers preventing credential use even if discovered.
🎯 Exploit Status
Exploitation requires discovering the hard-coded credentials, which may be found in documentation, code analysis, or previous compromises. Once credentials are known, exploitation is trivial.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 25.3.0
Vendor Advisory: https://support.avantra.com/hc/en-us/articles/5352465121695-Security-Notice-Legacy-Built-In-User-Account-rtm
Restart Required: Yes
Instructions:
1. Backup current configuration. 2. Download and install Avantra version 25.3.0 or later from official vendor sources. 3. Restart Avantra services. 4. Verify the 'rtm' account is no longer present or has randomized credentials.
🔧 Temporary Workarounds
Network Isolation
allRestrict network access to Avantra interfaces to only trusted administrative networks
Credential Rotation
allManually change credentials for all built-in accounts if possible
🧯 If You Can't Patch
- Implement strict network access controls to limit who can reach Avantra interfaces
- Enable additional authentication layers (MFA, IP whitelisting) and monitor for unauthorized access attempts
🔍 How to Verify
Check if Vulnerable:
Check Avantra version via web interface or command line. If version is below 25.3.0, the system is vulnerable. Also check for existence of 'rtm' user account.Check Version:
avantra --version or check web interface admin panelVerify Fix Applied:
After upgrading to 25.3.0+, verify version shows 25.3.0 or higher and attempt to authenticate with known hard-coded credentials (should fail).📡 Detection & Monitoring
Log Indicators:
- Failed authentication attempts for 'rtm' user
- Successful logins from unexpected IP addresses
- Unusual administrative actions performed
Network Indicators:
- Authentication requests to Avantra interfaces from unauthorized networks
- Traffic patterns indicating credential brute-forcing
SIEM Query:
source="avantra" AND (event_type="authentication" AND user="rtm") OR (event_type="admin_action" AND src_ip NOT IN allowed_admin_ips)