1. Introduction
Buffalo Routers are affected by multiple vulnerabilities (TRA-2021-13) that could allow attackers to bypass authentication, alter device configuration, and access sensitive information remotely. These vulnerabilities impact network security and potentially compromise the confidentiality, integrity, and availability of connected systems. Affected devices typically include home and small office routers. Impact on confidentiality is likely if sensitive data is exposed; integrity is impacted by potential configuration changes; and availability may be affected by denial-of-service or device malfunction.
2. Technical Explanation
The vulnerabilities stem from flaws in the web interfaces of certain Buffalo router models. A path traversal vulnerability (CVE-2021-20090) allows unauthenticated attackers to access files outside their intended directory, potentially bypassing authentication. Additionally, improper input sanitization (CVE-2021-20091) permits authenticated attackers to modify device configurations and potentially execute code. Finally, unrestricted access to sensitive information (CVE-2021-20092) exposes data to unauthorized actors. An attacker could exploit these vulnerabilities by sending crafted HTTP requests to the router’s web interface.
- Root cause: Missing input validation and insufficient access controls in the web interfaces of affected Buffalo routers.
- Exploit mechanism: Attackers can send malicious requests to the web interface, exploiting path traversal or leveraging improper sanitization to alter device settings.
- Scope: Certain Buffalo router models are affected. Specific model numbers should be confirmed with the vendor.
3. Detection and Assessment
To confirm vulnerability, check the router’s firmware version. A thorough assessment involves using a vulnerability scanner or manually inspecting web interface configurations for insecure settings.
- Quick checks: Access the router’s web management interface and check the firmware version under System Information or similar section.
- Scanning: Nessus vulnerability scan with plugin ID 15698 can detect these vulnerabilities, but relies on self-reported version numbers. Other scanners may have relevant signatures.
- Logs and evidence: Examine router logs for suspicious activity related to web interface access attempts or configuration changes. Specific log locations vary by model.
# Example command placeholder:
# No direct command available, check the web UI under System Information
4. Solution / Remediation Steps
Apply vendor-released fixes for affected models. Contact Buffalo support to obtain the appropriate firmware update.
4.1 Preparation
- Ensure a stable power supply during the update process. A roll back plan involves restoring the previous configuration if the update fails or causes issues.
- A change window may be required depending on network impact and business needs. Approval from IT management is recommended.
4.2 Implementation
- Step 1: Download the latest firmware for your specific Buffalo router model from the vendor’s website.
- Step 2: Log in to the router’s web management interface as an administrator.
- Step 3: Navigate to the Firmware Update or System Update section.
- Step 4: Upload the downloaded firmware file and initiate the update process.
4.3 Config or Code Example
Before
# No specific config example available, as this is a firmware vulnerability. Check vendor documentation for configuration changes related to security settings.
After
# After applying the update, verify the firmware version has been updated and that no default credentials are present.
4.4 Security Practices Relevant to This Vulnerability
Implementing least privilege can limit the impact of an attacker gaining access. Input validation prevents malicious data from being processed. A regular patch cadence ensures timely application of security updates.
- Practice 1: Least privilege reduces the potential damage if an attacker compromises a user account or service.
- Practice 2: Input validation blocks malicious requests and prevents exploitation of vulnerabilities like improper sanitization.
4.5 Automation (Optional)
No suitable automation script is available for this vulnerability due to the nature of firmware updates.
5. Verification / Validation
Confirm the fix by checking the router’s updated firmware version and re-running a vulnerability scan. Perform basic service smoke tests to ensure functionality remains intact.
- Post-fix check: Access the router’s web management interface and verify that the firmware version has been updated to the latest available release.
- Re-test: Run Nessus or another vulnerability scanner to confirm that the vulnerabilities are no longer detected.
- Monitoring: Monitor router logs for any unusual activity related to web interface access or configuration changes.
# Example command placeholder:
# No direct command available, check the web UI under System Information
6. Preventive Measures and Monitoring
- Baselines: Update security configuration standards or policies to require the latest firmware version for all Buffalo routers.
- Asset and patch process: Implement a regular schedule for reviewing and applying security updates to all network devices, including Buffalo routers.
7. Risks, Side Effects, and Roll Back
- Risk or side effect 1: Firmware update failure could render the router unusable. Mitigation: Back up configuration and have a replacement router available.
- Risk or side effect 2: Update may cause temporary network disruption. Mitigation: Schedule updates during off-peak hours.
- Roll back: 1) Reboot the router. 2) If the update failed, attempt to restore from the backup configuration file via the web interface. 3) Contact vendor support if restoration fails.
8. References and Resources
- Vendor advisory or bulletin: https://www.tenable.com/security/research/tra-2021-13
- NVD or CVE entry: CVE-2021-20090, CVE-2021-20091, CVE-2021-20092
- Product or platform documentation relevant to the fix: Check Buffalo’s official support website for specific firmware updates and instructions.