CVE-2024-23110: Fortinet FortiOS Buffer Overflow Flaw

CVE-2024-23110 Overview

CVE-2024-23110 is a stack-based buffer overflow vulnerability affecting Fortinet FortiOS, the operating system powering FortiGate network security appliances. This memory corruption flaw allows an authenticated local attacker to execute unauthorized code or commands by sending specially crafted commands to the affected system. The vulnerability impacts multiple versions of FortiOS across the 6.x and 7.x release branches, potentially affecting a wide range of enterprise network security deployments.

Critical Impact

Successful exploitation of this stack-based buffer overflow could allow attackers with local access to execute arbitrary code, potentially compromising the integrity and security of FortiGate appliances and the networks they protect.

Affected Products

• Fortinet FortiOS 7.4.0 through 7.4.2
• Fortinet FortiOS 7.2.0 through 7.2.6
• Fortinet FortiOS 7.0.0 through 7.0.13
• Fortinet FortiOS 6.4.0 through 6.4.14
• Fortinet FortiOS 6.2.0 through 6.2.15
• Fortinet FortiOS 6.0 all versions

Discovery Timeline

• June 11, 2024 - CVE-2024-23110 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-23110

Vulnerability Analysis

This vulnerability is classified under CWE-121 (Stack-based Buffer Overflow) and CWE-787 (Out-of-bounds Write). The flaw exists in the command processing functionality of FortiOS, where insufficient bounds checking on user-supplied input allows data to be written beyond the boundaries of an allocated stack buffer.

Stack-based buffer overflows are particularly dangerous as they can allow attackers to overwrite critical stack data, including return addresses and saved frame pointers. When exploited successfully, an attacker can redirect program execution to malicious code, achieving arbitrary code execution within the context of the vulnerable process.

The local attack vector requires the attacker to have some level of authenticated access to the FortiOS CLI or management interface. However, once this prerequisite is met, the low attack complexity and lack of required user interaction make exploitation straightforward for a skilled attacker.

Root Cause

The root cause of CVE-2024-23110 is improper input validation in the FortiOS command processing subsystem. When processing certain CLI commands, the system fails to adequately verify the length of user-supplied input before copying it into a fixed-size stack buffer. This allows an attacker to provide input exceeding the buffer's capacity, resulting in adjacent stack memory being overwritten with attacker-controlled data.

Attack Vector

The attack requires local access to the FortiOS system, typically through the CLI interface or management console. An authenticated attacker can craft malicious commands containing payloads designed to overflow the vulnerable stack buffer. The specially crafted input overwrites the return address on the stack, enabling the attacker to redirect execution flow to arbitrary code.

The exploitation chain typically involves:

1. Gaining authenticated access to the FortiOS CLI
2. Identifying the vulnerable command processing function
3. Crafting a malicious payload that overflows the stack buffer
4. Overwriting the return address to redirect execution
5. Achieving arbitrary code or command execution on the target system

For detailed technical information about this vulnerability, refer to the FortiGuard Security Advisory.

Detection Methods for CVE-2024-23110

Indicators of Compromise

• Unusual or malformed CLI commands in FortiOS logs
• Unexpected process crashes or system instability on FortiGate appliances
• Anomalous command execution patterns from authenticated sessions
• Evidence of memory corruption in system diagnostics

Detection Strategies

• Monitor FortiOS diagnostic logs for signs of buffer overflow attempts or memory corruption events
• Implement CLI command auditing to detect unusually long or malformed input strings
• Deploy behavioral analysis to identify anomalous command execution patterns from authenticated users
• Review authentication logs for suspicious login activity preceding potential exploitation attempts

Monitoring Recommendations

• Enable comprehensive logging on FortiOS management interfaces and CLI sessions
• Configure SIEM integration to correlate FortiOS events with other network security telemetry
• Establish baseline normal command patterns and alert on significant deviations
• Monitor system stability metrics that may indicate exploitation attempts

How to Mitigate CVE-2024-23110

Immediate Actions Required

• Upgrade FortiOS to the latest patched version immediately
• Restrict CLI and management interface access to trusted administrators only
• Implement network segmentation to limit exposure of FortiGate management interfaces
• Review and audit user accounts with access to FortiOS CLI functions

Patch Information

Fortinet has released security patches addressing this vulnerability. Organizations should upgrade to the following fixed versions based on their current deployment:

• FortiOS 7.4.3 or later for 7.4.x deployments
• FortiOS 7.2.7 or later for 7.2.x deployments
• FortiOS 7.0.14 or later for 7.0.x deployments
• FortiOS 6.4.15 or later for 6.4.x deployments

For complete patch information and upgrade guidance, consult the FortiGuard Security Advisory FG-IR-23-460.

Workarounds

• Restrict management interface access to specific trusted IP addresses using FortiOS access control features
• Implement multi-factor authentication for all administrative access to FortiGate devices
• Disable unused CLI commands where possible to reduce attack surface
• Segment management networks from general user traffic

# Example: Restrict management access to trusted hosts
config system admin
    edit "admin"
        set trusthost1 10.0.0.0 255.255.255.0
        set trusthost2 192.168.1.0 255.255.255.0
    next
end