1. Introduction
The OpenLink Web Configurator GET Request Remote Overflow vulnerability affects a web server application due to its handling of overly long requests. This can lead to denial of service, potentially disrupting business operations and impacting system availability. Systems running the affected OpenLink Web Configurator are at risk. A successful exploit could crash the server or allow an attacker to run code on it, affecting confidentiality, integrity, and availability.
2. Technical Explanation
The vulnerability occurs because the web application does not properly validate the length of GET requests received by its Web Configurator. An attacker can send a request exceeding the buffer size allocated for processing, causing a crash. This is known as a buffer overflow. CVE-1999-0943 details this issue.
- Root cause: Insufficient input validation on GET requests received by the Web Configurator application.
- Exploit mechanism: An attacker sends an HTTP GET request with a very long URI, exceeding the buffer size of the web server’s processing logic. This can be done using tools like curl or a web browser. For example, sending a request such as
http://target/webconfigurator?A=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...(repeated ‘A’ characters) could trigger the overflow. - Scope: Affected systems are those running OpenLink Web Configurator. Specific versions were not identified in available documentation.
3. Detection and Assessment
Confirming vulnerability requires checking the version of the installed Web Configurator application and monitoring for crashes during high request loads.
- Quick checks: Check the OpenLink Web Configurator’s about page or configuration files to determine its version number.
- Scanning: Nessus plugin ID 20876 may identify this vulnerability, but results should be verified manually.
- Logs and evidence: Monitor web server logs (e.g., Apache access/error logs) for crashes or errors related to the Web Configurator application during periods of high request volume. Look for segmentation faults or similar error messages.
# Example command placeholder:
# No specific command available without knowing the OS and web server configuration. Check web server logs as described above.
4. Solution / Remediation Steps
Currently, a direct solution or patch is not known for this vulnerability. Mitigation focuses on limiting exposure and monitoring.
4.1 Preparation
- Dependencies: No specific dependencies are known. Roll back plan: Restore the web server configuration from backup or revert the system snapshot.
- Change window needs: A standard change window is recommended, with approval from the IT security team.
4.2 Implementation
- Step 1: Implement input validation on all GET requests to limit the maximum URI length accepted by the web server. This may require modifying application code or using a web application firewall (WAF).
- Step 2: Configure the web server to reject requests exceeding a reasonable size threshold.
4.3 Config or Code Example
Before
# No specific configuration example available as this is an application-level vulnerability. Typically, there would be no explicit code limiting request size.
After
# Example Apache configuration (adjust for your web server):
# LimitRequestFieldsLimit 8190
# This limits the total size of all request headers to 8KB, which can help prevent excessively long URIs.
4.4 Security Practices Relevant to This Vulnerability
Several security practices can mitigate this type of vulnerability.
- Practice 2: Least privilege limits the impact if an attacker exploits a vulnerability by reducing the permissions available to compromised processes.
4.5 Automation (Optional)
No specific automation script is available for this vulnerability due to its application-level nature.
# No suitable script available. Consider using WAF rules or configuration management tools to enforce input validation policies.
5. Verification / Validation
Confirm the fix by attempting to send a long GET request and verifying that it is blocked or handled safely.
- Post-fix check: Attempt to access
http://target/webconfigurator?A=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...(repeated ‘A’ characters). The server should return an error message indicating the request is too large, or handle the request without crashing. - Re-test: Re-run the earlier detection method by monitoring web server logs during a high request load to ensure no crashes occur.
- Monitoring: Monitor web server logs for errors related to request processing, specifically looking for rejected requests due to size limits or input validation failures.
# Post-fix command and expected output:
# curl -I http://target/webconfigurator?A=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...
# Expected Output: HTTP/1.1 400 Bad Request (or similar error message)
6. Preventive Measures and Monitoring
Proactive measures can reduce the risk of similar vulnerabilities.
- Baselines: Update security baselines to include input validation requirements for all web applications.
- Pipelines: Integrate Static Application Security Testing (SAST) tools into CI/CD pipelines to identify potential buffer overflows during development.
- Asset and patch process: Implement a regular vulnerability scanning schedule to identify and address known vulnerabilities in web application components.
7. Risks, Side Effects, and Roll Back
Implementing input validation may cause compatibility issues with legitimate applications that rely on long URLs.
- Risk or side effect 1: Overly strict input validation could block valid requests. Mitigation: Carefully test the changes to ensure no disruption of normal functionality.
- Roll back: Restore the web server configuration from backup or revert the system snapshot if any issues occur. Remove any WAF rules that were added.
8. References and Resources
Links related to this specific vulnerability.
- Vendor advisory or bulletin: No official vendor advisory was found at time of writing.
- NVD or CVE entry: https://nvd.nist.gov/vuln/detail/CVE-1999-0943
- Product or platform documentation relevant to the fix: No specific documentation found for this vulnerability, but general web server configuration guides may be helpful.