CVE-2023-45583: Fortinet FortiProxy RCE Vulnerability

CVE-2023-45583 Overview

CVE-2023-45583 is a format string vulnerability affecting multiple Fortinet security products including FortiProxy, FortiPAM, FortiOS, and FortiSwitchManager. The vulnerability exists due to the use of externally-controlled format strings in the affected components, which allows authenticated attackers with high privileges to execute unauthorized code or commands via specially crafted CLI commands and HTTP requests.

Critical Impact

Authenticated attackers can achieve complete system compromise through arbitrary code execution on affected Fortinet network security appliances, potentially leading to full network takeover.

Affected Products

• Fortinet FortiProxy versions 7.2.0 through 7.2.5, 7.0.0 through 7.0.11, 2.0.0 through 2.0.13, 1.2.0 through 1.2.13, and 1.1.0 through 1.1.6
• Fortinet FortiPAM versions 1.1.0 and 1.0.0 through 1.0.3
• Fortinet FortiOS versions 7.4.0, 7.2.0 through 7.2.5, 7.0.0 through 7.0.13, 6.4.0 through 6.4.14, and 6.2.0 through 6.2.15
• Fortinet FortiSwitchManager versions 7.2.0 through 7.2.2 and 7.0.0 through 7.0.2

Discovery Timeline

• 2024-05-14 - CVE-2023-45583 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-45583

Vulnerability Analysis

This vulnerability is classified as CWE-134 (Use of Externally-Controlled Format String). Format string vulnerabilities occur when user-supplied input is used directly as the format specifier in functions like printf(), sprintf(), or similar formatting functions without proper sanitization.

In the case of CVE-2023-45583, the affected Fortinet products improperly handle format specifiers in user-controlled input through CLI commands and HTTP request parameters. An attacker with administrative privileges can craft malicious input containing format specifiers such as %s, %x, %n, or similar tokens that the underlying formatting functions interpret as instructions rather than literal text.

The attack requires network access and high privileges (administrative authentication), but once these conditions are met, successful exploitation can lead to complete confidentiality, integrity, and availability compromise of the target system.

Root Cause

The root cause of CVE-2023-45583 is insufficient input validation and sanitization when handling user-supplied data in formatting functions. The affected Fortinet products fail to properly escape or validate format specifiers in input received through the command-line interface and HTTP API endpoints.

When user-controlled input containing format string specifiers is passed directly to formatting functions, the application processes these specifiers as formatting instructions. This allows attackers to read from or write to arbitrary memory locations, potentially leading to information disclosure, denial of service, or arbitrary code execution.

Attack Vector

The attack vector for CVE-2023-45583 requires network access to the management interface of affected Fortinet products. An attacker must have high-level administrative privileges to interact with the vulnerable CLI commands or HTTP endpoints. The exploitation process involves:

1. Authenticating to the Fortinet device with administrative credentials
2. Crafting malicious input containing format string specifiers (e.g., %x to read stack memory, %n to write to memory)
3. Submitting the payload through vulnerable CLI commands or HTTP requests
4. The format string specifiers are processed by the underlying formatting functions, allowing memory manipulation

Due to the privileged access requirement, this vulnerability is most likely to be exploited in scenarios involving compromised administrator credentials, insider threats, or chained attacks where initial access has already been established.

Detection Methods for CVE-2023-45583

Indicators of Compromise

• Unusual CLI commands containing multiple percent signs (%) followed by format specifiers (x, s, n, p)
• HTTP requests to management interfaces containing encoded format string patterns in parameters
• Unexpected application crashes or behavior anomalies on Fortinet management interfaces
• Memory access violations or segmentation faults in system logs

Detection Strategies

• Monitor Fortinet device logs for malformed CLI commands containing suspicious format string patterns
• Implement network monitoring for HTTP requests to management interfaces with unusual percent-encoded sequences
• Deploy intrusion detection rules to identify format string attack patterns targeting Fortinet management services
• Enable verbose logging on Fortinet devices to capture detailed command execution history

Monitoring Recommendations

• Configure SIEM alerts for authentication events followed by suspicious CLI activity on Fortinet devices
• Implement network segmentation monitoring to detect unauthorized access attempts to management interfaces
• Establish baseline behavior for administrative sessions and alert on deviations
• Monitor for multiple failed authentication attempts followed by successful login, which may indicate credential compromise

How to Mitigate CVE-2023-45583

Immediate Actions Required

• Review and apply the latest security patches from Fortinet for all affected products
• Restrict network access to management interfaces using firewall rules and VPN requirements
• Audit administrative accounts and remove unnecessary privileged access
• Enable multi-factor authentication for all administrative access to Fortinet devices

Patch Information

Fortinet has released security patches addressing CVE-2023-45583. Organizations should consult the FortiGuard Security Advisory FG-IR-23-137 for detailed patch information and upgrade guidance specific to their deployed product versions. Upgrade to the latest supported version of each affected product to ensure comprehensive protection against this vulnerability.

Workarounds

• Implement strict network access controls limiting management interface exposure to trusted administrative workstations only
• Deploy web application firewall rules to filter format string attack patterns in HTTP requests
• Use jump servers or bastion hosts for all administrative access to reduce direct exposure
• Consider disabling unused management interfaces (HTTP/HTTPS or CLI) where possible

# Example: Restrict management access to trusted networks
config system interface
    edit "mgmt"
        set allowaccess ping https ssh
        set trust-ip1 10.0.0.0/8
    next
end

# Enable administrative access logging
config log setting
    set admin-log enable
end