1. Introduction
RSA ClearTrust ct_logon.asp is vulnerable to a cross-site scripting attack, allowing an attacker to inject malicious scripts into web pages viewed by users. This can lead to session hijacking, defacement of websites, or redirection to harmful sites. Systems running the RSA ClearTrust web server are affected. A successful exploit could compromise confidentiality, integrity and availability of user sessions and data.
2. Technical Explanation
The vulnerability stems from insufficient input validation in the ‘ct_logon.asp’ or ‘ct_logon.jsp’ scripts. An attacker can craft a malicious URL containing XSS payloads that are then executed by unsuspecting users’ browsers. The attack is remote, meaning it does not require access to the server itself. CWE-20 (Improper Input Validation) and related CWEs apply here.
- Root cause: Missing or inadequate sanitisation of user input passed to ‘ct_logon.asp’ or ‘ct_logon.jsp’.
- Exploit mechanism: An attacker crafts a URL with a malicious script in one of the parameters, then tricks a user into visiting it. For example:
http://example.com/ct_logon.asp?parameter= - Scope: RSA ClearTrust web servers are affected. Specific versions were not identified in available information.
3. Detection and Assessment
Confirming vulnerability requires checking the version of ClearTrust installed, and testing for XSS via crafted URLs.
- Quick checks: Check the RSA ClearTrust web server’s ‘About’ page or configuration files to determine its version.
- Scanning: Nessus plugin ID 30198 may detect this vulnerability as an example.
- Logs and evidence: Examine web server logs for suspicious URL parameters containing script tags or encoded characters. Look for requests targeting ‘ct_logon.asp’ or ‘ct_logon.jsp’.
4. Solution / Remediation Steps
Currently there is no known solution for this vulnerability at the time of writing. Mitigation should focus on input validation and output encoding.
4.1 Preparation
- Ensure you have access to the ClearTrust configuration files. A roll back plan involves restoring from the pre-change backup.
- Change windows may be needed depending on business impact, and should be approved by IT management.
4.2 Implementation
- Step 1: Review all code related to ‘ct_logon.asp’ or ‘ct_logon.jsp’.
- Step 2: Implement strict input validation on all parameters passed to these scripts, rejecting any input containing script tags or potentially malicious characters.
- Step 4: Thoroughly test the changes with a variety of inputs to ensure they do not break functionality and effectively block XSS attempts.
4.3 Config or Code Example
Before
<% Response.Write Request("parameter") %>After
<% Response.Write Server.HTMLEncode(Request("parameter")) %>4.4 Security Practices Relevant to This Vulnerability
Practices that directly address this vulnerability type include input validation and least privilege.
- Practice 1: Input validation prevents malicious data from being processed by the server, mitigating XSS attacks.
- Practice 2: Least privilege limits the impact of a successful exploit by restricting the attacker’s access to sensitive resources.
4.5 Automation (Optional)
No automation is provided due to the lack of a specific fix and the need for code review.
5. Verification / Validation
Confirming the fix requires re-testing with crafted URLs to ensure XSS attempts are blocked and that core functionality remains intact.
- Post-fix check: Verify that attempting to inject a script tag in a URL parameter no longer executes JavaScript code in the browser.
- Re-test: Repeat the earlier detection method (attempting an XSS attack) to confirm it is now unsuccessful.
- Monitoring: Monitor web server logs for any suspicious URL parameters or failed login attempts as a baseline.
6. Preventive Measures and Monitoring
Update security baselines to include input validation requirements, and add checks in CI/CD pipelines to prevent XSS vulnerabilities from being deployed.
- Baselines: Update your web application security baseline to require strict input validation on all user-supplied data.
- Pipelines: Integrate Static Application Security Testing (SAST) tools into your CI/CD pipeline to identify potential XSS vulnerabilities during development.
- Asset and patch process: Implement a regular review cycle for security patches and configuration changes, ensuring timely updates to address known vulnerabilities.
7. Risks, Side Effects, and Roll Back
Implementing input validation may cause compatibility issues with existing applications or require code modifications. A roll back plan involves restoring from the pre-change backup.
- Risk or side effect 1: Strict input validation could break existing functionality that relies on specific characters in user input. Mitigation involves careful testing and adjusting validation rules as needed.
- Risk or side effect 2: Code modifications may introduce new bugs or vulnerabilities. Mitigation involves thorough code review and testing.
- Roll back: Restore the ClearTrust server from the pre-change backup to return to the previous state.
8. References and Resources
- Vendor advisory or bulletin: https://seclists.org/bugtraq/2003/Mar/214
- NVD or CVE entry: No specific CVE identified for this vulnerability.
- Product or platform documentation relevant to the fix: RSA ClearTrust documentation on input validation and output encoding.