1. Introduction
The WindWeb <= 2.0 Malformed GET Request Remote Denial of Service vulnerability affects web servers running on embedded devices, commonly found in ADSL modems and routers from Wind River Systems. A malicious actor can send specially crafted requests to the server, causing it to become unresponsive and denying service to legitimate users. This impacts the availability of affected services.
2. Technical Explanation
The vulnerability stems from insufficient input validation when handling GET requests. An attacker can exploit this by sending a request with an abnormally long or malformed URI, exceeding the server’s buffer capacity and leading to a crash. The Common Vulnerabilities and Exposures (CVE) identifier for this issue is CVE-2005-3475.
- Root cause: Missing input validation on GET request URIs allows excessively long requests.
- Exploit mechanism: An attacker sends an HTTP GET request with a very long URI to the vulnerable WindWeb server. This overwhelms the server’s resources, causing it to stop responding. For example:
GET /AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA HTTP/1.0 - Scope: Affected platforms are embedded devices running WindWeb version 2.0 and earlier on VxWorks operating systems.
3. Detection and Assessment
You can confirm vulnerability by checking the installed WindWeb version. A thorough assessment involves attempting to trigger the denial of service.
- Quick checks: Use the web server’s header information or configuration page (if accessible) to identify the WindWeb version.
- Scanning: Nessus plugin ID 30981 may detect this vulnerability, but results should be verified manually.
# Example command placeholder:
# No direct command available without access to the target device's shell. Check HTTP headers via a browser developer tool.
4. Solution / Remediation Steps
Limit access to the web server and apply updates if available.
4.1 Preparation
- Dependencies: Access to the device’s configuration interface is required. Roll back plan: Restore the previous configuration or snapshot.
- Change window needs: A maintenance window may be needed depending on the impact of stopping the web service. Approval from the system owner is recommended.
4.2 Implementation
- Step 1: Restrict access to the WindWeb web server using firewall rules, allowing only trusted IP addresses or networks.
- Step 2: If a newer version of WindWeb is available from Wind River Systems, upgrade to that version following their official instructions.
4.3 Config or Code Example
Before
# No specific configuration example available, as access control is typically managed via firewall rules. Assume unrestricted access by default.
After
# Example Firewall Rule (iptables):
# iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
# iptables -A INPUT -p tcp --dport 80 -j DROP
4.4 Security Practices Relevant to This Vulnerability
List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence.
- Practice 1: Least privilege – Restrict network access to the web server to reduce the attack surface.
- Practice 2: Input Validation – Implement robust input validation on all incoming requests to prevent malformed data from reaching the server.
4.5 Automation (Optional)
# No automation script provided due to device-specific configuration requirements. Consider using network management tools to enforce firewall rules consistently.
5. Verification / Validation
Confirm the fix by checking access restrictions and attempting to trigger the denial of service again.
- Post-fix check: Verify that only allowed IP addresses can reach the web server on port 80 (or the relevant port).
- Re-test: Attempt to send a long GET request from an unallowed IP address. The request should be blocked by the firewall.
- Smoke test: Ensure legitimate users can still access essential web services if allowed by the firewall rules.
- Monitoring: Monitor web server logs for blocked requests originating from untrusted sources.
# Example Firewall Rule Check (iptables):
# iptables -L INPUT | grep 80
6. Preventive Measures and Monitoring
Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.
- Baselines: Update security baselines or policies to include restrictions on network access to web servers.
- Pipelines: Implement input validation checks in CI/CD pipelines for any custom web applications running on the device.
- Asset and patch process: Establish a regular patch review cycle, especially for embedded devices, to address known vulnerabilities promptly.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 2: Service interruption during upgrade process (if applicable). Mitigation: Perform upgrades during a maintenance window and have a roll back plan in place.
- Roll back: Remove the firewall rules to restore unrestricted access, or revert to the previous configuration snapshot.
8. References and Resources
- Vendor advisory or bulletin: https://downloads.securityfocus.com/vulnerabilities/exploits/Hasbani_dos.c
- NVD or CVE entry: CVE-2005-3475
- Product or platform documentation relevant to the fix: No specific documentation available beyond vendor advisories.