1. Introduction
The CMS Made Simple admin/login.php cms_language Cookie Local File Inclusion vulnerability allows an unauthenticated attacker to view arbitrary files on a vulnerable web server, and potentially execute PHP code with the privileges of the web server user. This affects content management systems running CMS Made Simple. Successful exploitation could lead to information disclosure or remote code execution. The likely impact is high confidentiality, medium integrity, and low availability.
2. Technical Explanation
- Exploit mechanism: An attacker crafts a malicious request containing a specially crafted ‘cms_language’ cookie value that points to a local file on the server. This allows them to include and execute arbitrary files. For example, setting the cms_language cookie to `/etc/passwd`.
- Scope: CMS Made Simple versions prior to the fix are affected.
3. Detection and Assessment
You can confirm a system is vulnerable by checking the installed version of CMS Made Simple and attempting to exploit the vulnerability in a test environment.
- Quick checks: Access the CMS Made Simple admin interface and check the ‘About’ section for the version number.
- Scanning: Nessus plugin ID 32535 can detect this vulnerability. This is an example only, other scanners may also identify it.
- Logs and evidence: Check web server access logs for requests to admin/login.php with suspicious ‘cms_language’ cookie values. Look for attempts to include files outside the expected CMS Made Simple directories.
# Example command placeholder:
# No direct command available, check version via UI or source code review.
4. Solution / Remediation Steps
Currently there is no known solution at this time. Mitigation should focus on preventing access to the vulnerable script and monitoring for exploitation attempts.
4.1 Preparation
- No services need to be stopped at this time, but monitor closely during testing. A roll back plan is to restore from backup.
- Change windows may be required depending on business impact and testing results. Approval should be obtained from IT security or system owners.
4.2 Implementation
- Step 1: Implement web application firewall (WAF) rules to block requests containing suspicious ‘cms_language’ cookie values.
- Step 2: Monitor web server logs for exploitation attempts and investigate any unusual activity.
- Step 3: Regularly update CMS Made Simple when a patch becomes available.
4.3 Config or Code Example
Before
# No code example available as there is no known patch. This vulnerability exists due to improper input validation in admin/login.php.
After
# No code example available as there is no known patch. Implement WAF rules to block malicious requests.
4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this type of vulnerability. Input validation is crucial for blocking unsafe data. Least privilege reduces the impact if an attacker gains access. Patch cadence ensures timely updates and fixes. Safe defaults minimise the attack surface.
- Practice 1: Implement strict input validation on all user-supplied data to prevent malicious code injection.
- Practice 2: Apply the principle of least privilege to limit the permissions of the web server user account.
4.5 Automation (Optional)
No automation is available as there is no known patch. WAF rules can be automated using a configuration management tool.
# Example Bash script for blocking requests with suspicious cookie values in Apache:
# iptables -A INPUT -p tcp --dport 80 -m string --string "cms_language=/etc/passwd" --algo bm -j DROP
# Note: This is a basic example and may require adjustments based on your environment.
5. Verification / Validation
- Post-fix check: Attempt to access admin/login.php with a malicious ‘cms_language’ cookie value (e.g., /etc/passwd). The request should be blocked by the WAF or other mitigation measures.
- Re-test: Review web server logs for failed requests containing suspicious cookie values, confirming that the attack is no longer successful.
- Monitoring: Monitor web server access logs for any attempts to exploit the vulnerability or include files outside of expected directories.
# Post-fix command and expected output:
# Attempting to access admin/login.php with a malicious cookie should result in an HTTP 403 Forbidden error, indicating that the request was blocked by the WAF.
6. Preventive Measures and Monitoring
Update security baselines to include input validation requirements for web applications. Implement checks in CI/CD pipelines to scan code for potential vulnerabilities. Establish a regular patch or configuration review cycle to ensure timely updates.
- Baselines: Update your security baseline to require strict input validation on all user-supplied data, including cookies.
- Pipelines: Add Static Application Security Testing (SAST) tools to your CI/CD pipeline to scan code for potential vulnerabilities like local file inclusion.
- Asset and patch process: Implement a regular patch review cycle of at least monthly to ensure that CMS Made Simple is updated with the latest security fixes.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: False positives from WAF rules may block legitimate user traffic. Mitigation is to fine-tune the WAF rules based on observed traffic patterns.
- Roll back: Remove or disable the implemented WAF rules to restore normal operation. Restore from backup if necessary.
8. References and Resources
- Vendor advisory or bulletin: CMS Made Simple Security Advisories
- NVD or CVE entry: CVE-2008-5642
- Product or platform documentation relevant to the fix: No specific documentation available as there is no patch.