1. Introduction
The Citrix Access Gateway Administrative Web Interface uses default credentials, allowing unauthorized access to administrative functions. This vulnerability allows attackers to gain control of affected servers and potentially upload malicious system images. Systems running the Citrix Access Gateway with default credentials are at risk, impacting confidentiality, integrity, and availability.
2. Technical Explanation
The remote web application is shipped with pre-configured usernames and passwords for the administrative interface. If these default credentials have not been changed, an attacker can log in remotely and gain full control of the system. This could allow them to modify configurations or upload malicious content.
- Root cause: Use of hardcoded default credentials.
- Exploit mechanism: An attacker attempts to login using common default usernames and passwords. Successful authentication grants administrative access. For example, an attacker might use the username ‘admin’ with a known default password.
- Scope: Citrix Access Gateway administrative web interface.
3. Detection and Assessment
To confirm vulnerability, check if default credentials are still in use. A thorough method involves attempting to log in with common default usernames and passwords.
- Quick checks: Check the configuration for any accounts named ‘admin’ or similar.
- Scanning: Nessus plugin ID 138695 can detect this vulnerability. This is an example only, other scanners may also provide detection capabilities.
- Logs and evidence: Examine authentication logs for successful logins using default credentials.
4. Solution / Remediation Steps
The solution involves changing the default credentials immediately. Follow these steps to fix the issue.
4.1 Preparation
- Dependencies: Ensure you have administrative access to the Citrix Access Gateway web interface. Roll back plan: Restore from backup if issues occur.
- Change window needs: This should be done during a maintenance window, with approval from system owners.
4.2 Implementation
- Step 1: Log in to the Citrix Access Gateway administrative web interface.
- Step 2: Navigate to Users > Accounts.
- Step 3: Locate any accounts using default usernames (e.g., admin).
- Step 4: Change the password for these accounts to strong, unique values.
- Step 5: Verify that new passwords are functioning correctly by attempting to log in with them.
4.3 Config or Code Example
Before
Account Name: admin
Password: password
After
Account Name: admin
Password: StrongUniquePassword!
4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this issue. Least privilege reduces impact if an account is compromised, and safe defaults ensure systems are configured securely out-of-the-box.
- Practice 1: Implement least privilege by granting only necessary permissions to accounts.
- Practice 2: Enforce strong password policies and regular password changes.
4.5 Automation (Optional)
Automation is not recommended for this task due to the risk of locking out administrative access if misconfigured.
5. Verification / Validation
Confirm that default credentials no longer work and new passwords are required for login. Perform a service smoke test to ensure functionality remains intact.
- Post-fix check: Attempt to log in with the previous default username and password; authentication should fail.
- Re-test: Repeat the earlier detection steps, which should no longer identify the vulnerability.
- Smoke test: Verify that administrative users can still access and manage the Citrix Access Gateway using their new credentials.
- Monitoring: Monitor authentication logs for failed login attempts with default credentials as an indicator of potential attacks.
Attempting to log in with username 'admin' and password 'password' should result in a "Invalid username or password" error.
6. Preventive Measures and Monitoring
Update security baselines to include requirements for changing default credentials on all systems. Implement CI/CD pipeline checks to prevent deployments with default settings.
- Baselines: Update a security baseline or policy to require immediate password changes for default accounts.
- Pipelines: Add checks in deployment pipelines to scan for and reject configurations using default credentials.
- Asset and patch process: Review configuration regularly as part of an asset management process.
7. Risks, Side Effects, and Roll Back
- Roll back: Restore the Citrix Access Gateway configuration from the pre-change backup if issues occur.
8. References and Resources
- Vendor advisory or bulletin: http://support.citrix.com/article/CTX129498