CVE-2024-46668: Fortinet FortiOS DoS Vulnerability

CVE-2024-46668 Overview

CVE-2024-46668 is a resource exhaustion vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Fortinet FortiOS network security operating system. This vulnerability allows an unauthenticated remote attacker to consume all available system memory by uploading multiple large files to the affected device, resulting in a denial of service condition.

Critical Impact

Unauthenticated remote attackers can exhaust system memory on FortiOS devices through repeated large file uploads, potentially causing complete service disruption for network security infrastructure.

Affected Products

• FortiOS versions 7.4.0 through 7.4.4
• FortiOS versions 7.2.0 through 7.2.8
• FortiOS versions 7.0.0 through 7.0.15
• FortiOS versions 6.4.0 through 6.4.15

Discovery Timeline

• 2025-01-14 - CVE-2024-46668 published to NVD
• 2025-01-31 - Last updated in NVD database

Technical Details for CVE-2024-46668

Vulnerability Analysis

This vulnerability stems from insufficient resource management in FortiOS's file handling mechanisms. When processing file uploads, the affected FortiOS versions fail to implement proper limits or throttling on memory allocation. This design flaw allows remote attackers to submit multiple large file upload requests without authentication, causing the system to allocate unbounded memory resources.

The attack requires network access to the FortiOS device and does not require any user interaction or authentication, making it particularly dangerous for internet-facing FortiGate appliances. The impact is limited to availability—there is no direct impact to confidentiality or integrity of data on the system. However, given that FortiOS devices typically serve as critical network security infrastructure (firewalls, VPN gateways, etc.), a successful denial of service attack could significantly impact an organization's security posture.

Root Cause

The root cause of CVE-2024-46668 is the absence of proper resource allocation controls in FortiOS's file upload handling functionality. The system does not enforce limits on the total memory that can be consumed by concurrent or sequential file upload operations. This allows an attacker to repeatedly send large file upload requests, with each request consuming additional system memory until the device becomes unresponsive or crashes.

Attack Vector

The attack is network-based and can be executed remotely without authentication. An attacker initiates the attack by sending multiple HTTP requests containing large file payloads to the vulnerable FortiOS device. Since there are no throttling mechanisms or memory caps in place, each upload consumes system memory proportional to the file size. By sending numerous large files in rapid succession, an attacker can exhaust the device's available memory, leading to denial of service.

The attack is relatively simple to execute and requires no specialized knowledge beyond the ability to send HTTP requests with large payloads. This low barrier to exploitation, combined with the lack of authentication requirements, makes this vulnerability particularly concerning for organizations with internet-exposed FortiGate appliances.

Detection Methods for CVE-2024-46668

Indicators of Compromise

• Abnormally high memory utilization on FortiOS devices without corresponding legitimate traffic increases
• Multiple large file upload requests from single or multiple source IP addresses in short time periods
• System performance degradation or unresponsiveness on FortiGate appliances
• Unexpected device reboots or service restarts related to memory exhaustion

Detection Strategies

• Configure SNMP monitoring to alert on memory utilization thresholds exceeding normal operational baselines
• Implement network traffic analysis to detect patterns of repeated large POST requests targeting FortiOS management interfaces
• Enable and review FortiOS system logs for memory allocation warnings or out-of-memory events
• Deploy intrusion detection rules to identify volumetric file upload patterns targeting FortiGate devices

Monitoring Recommendations

• Establish baseline memory utilization metrics for FortiOS devices and configure alerts for significant deviations
• Monitor network traffic logs for unusual volumes of inbound file uploads to FortiGate management interfaces
• Implement real-time alerting for FortiOS system health metrics including memory, CPU, and process status
• Consider deploying external health checks that can detect FortiOS device unavailability

How to Mitigate CVE-2024-46668

Immediate Actions Required

• Review the Fortinet PSIRT Advisory FG-IR-24-219 for specific remediation guidance
• Upgrade FortiOS to a patched version as specified in the vendor advisory
• Restrict network access to FortiOS management interfaces to trusted IP addresses only
• Implement rate limiting on upstream network devices to throttle large file upload requests

Patch Information

Fortinet has released security updates to address this vulnerability. Organizations should consult the Fortinet PSIRT Advisory FG-IR-24-219 for detailed patch information and upgrade paths. Upgrade to the following minimum versions:

• FortiOS 7.4.5 or later for the 7.4.x branch
• FortiOS 7.2.9 or later for the 7.2.x branch
• FortiOS 7.0.16 or later for the 7.0.x branch
• FortiOS 6.4.16 or later for the 6.4.x branch

Workarounds

• Restrict access to FortiOS management interfaces using firewall rules to allow only trusted administrator IP addresses
• Implement upstream rate limiting to throttle the number and size of file upload requests
• Deploy a web application firewall (WAF) in front of FortiOS devices to filter malicious upload attempts
• Consider temporarily disabling file upload functionality if not required for operations until patching is complete

# Example: Restrict management interface access to trusted networks
# Configure trusted hosts for admin access in FortiOS CLI
config system admin
    edit "admin"
        set trusthost1 192.168.1.0 255.255.255.0
        set trusthost2 10.0.0.0 255.0.0.0
    next
end