How Fortinet Tackles Unpatched Critical RCE Vectors

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Introduction

Fortinet has released critical patches for a vulnerability in its Wireless LAN Manager (FortiWLM) that could allow attackers to exploit unauthenticated sensitive information disclosure and enable remote code execution (RCE). The flaw, CVE-2023-34990, has a CVSS score of 9.6 and poses a serious risk, especially when combined with a previously patched bug, CVE-2023-48782.

Given Fortinet’s prominence as a key player in cybersecurity, this vulnerability highlights the need for swift action to secure affected systems.

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What Is CVE-2023-34990?

Key Details:

• Type: Unauthenticated limited file read vulnerability.
• Impact: Sensitive information disclosure, including access to authenticated user session IDs.
• Severity Score: 9.6 (Critical).

Vulnerable Versions:

• FortiWLM 8.6.0 to 8.6.5 (fixed in 8.6.6 or above).
• FortiWLM 8.5.0 to 8.5.4 (fixed in 8.5.5 or above).

This vulnerability arises from insufficient input validation on request parameters, enabling directory traversal and unauthorized access to system log files.

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The Exploit Chain: Combining CVE-2023-34990 and CVE-2023-48782

CVE-2023-34990 becomes even more dangerous when combined with another vulnerability, CVE-2023-48782, patched last year.

How the Exploit Works:

1. Log File Read:
   • CVE-2023-34990 enables attackers to access verbose system logs, exposing session IDs of authenticated users.
   • Using this information, attackers can access authenticated endpoints.
2. Command Injection:
   • CVE-2023-48782 allows an attacker to inject malicious commands via the /ems/cgi-bin/ezrf_switches.cgi endpoint.
   • These commands are executed with root privileges, leading to full system compromise.

Result:

By chaining the two vulnerabilities, attackers can achieve unauthenticated RCE in the context of root, posing a severe threat to affected systems.

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Risk to Organizations

Fortinet’s products are widely deployed across enterprise environments, making them a frequent target for attackers. Unpatched vulnerabilities like these are particularly dangerous for:

• Critical Infrastructure: Organizations relying on FortiWLM for secure wireless networking.
• Enterprise Networks: Businesses using Fortinet appliances for network management and security.

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Mitigation Steps

Administrators must act swiftly to secure their FortiWLM appliances.

1. Apply Patches Immediately:

• Update to:
  • 8.6.6 or above for FortiWLM versions 8.6.x.
  • 8.5.5 or above for FortiWLM versions 8.5.x.

2. Limit Access to Authenticated Endpoints:

• Restrict access to the /ems/cgi-bin/ezrf_switches.cgi endpoint and other critical areas.
• Use network segmentation to limit exposure.

3. Monitor for Indicators of Compromise (IOCs):

• Check system logs for unusual access patterns.
• Look for attempts to exploit log file reads or inject commands.

4. Harden Systems:

• Enforce strict input validation on all request parameters.
• Implement robust monitoring and intrusion detection systems to detect exploitation attempts.

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Insights from Researchers

Zach Hanley, a security researcher at Horizon3.ai, emphasized the criticality of this exploit chain:

“Combining both the unauthenticated arbitrary log file read and this authenticated command injection, an unauthenticated attacker can obtain remote code execution in the context of root. Admins should patch the Fortinet appliances ASAP.”

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Conclusion

The vulnerabilities in Fortinet’s Wireless LAN Manager highlight the critical importance of timely patching and proactive security measures. CVE-2023-34990, when combined with CVE-2023-48782, represents a significant risk to enterprise networks.

By applying the recommended patches and following best practices for securing network devices, organizations can mitigate these risks and protect their critical infrastructure from exploitation.

Stay vigilant, stay secure, and ensure your systems are up to date.

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