CVE-2025-31365: Fortinet FortiClient RCE Vulnerability

CVE-2025-31365 Overview

CVE-2025-31365 is an Improper Control of Generation of Code ('Code Injection') vulnerability (CWE-94) affecting FortiClientMac. This vulnerability allows an unauthenticated attacker to execute arbitrary code on a victim's macOS host by tricking the user into visiting a malicious website. The attack leverages improper code generation controls within the FortiClientMac application, enabling remote code execution through social engineering tactics.

Critical Impact

Unauthenticated remote attackers can achieve arbitrary code execution on macOS systems running vulnerable FortiClientMac versions by luring users to malicious websites, potentially leading to complete system compromise.

Affected Products

• FortiClientMac 7.4.0 through 7.4.3
• FortiClientMac 7.2.1 through 7.2.8
• Fortinet FortiClient for macOS

Discovery Timeline

• 2025-10-14 - CVE-2025-31365 published to NVD
• 2025-10-15 - Last updated in NVD database

Technical Details for CVE-2025-31365

Vulnerability Analysis

This vulnerability stems from improper control of code generation within FortiClientMac, classified under CWE-94 (Improper Control of Generation of Code). The flaw exists in how FortiClientMac processes certain inputs, allowing an attacker to inject and execute arbitrary code on the target system. The attack requires user interaction—specifically, the victim must be lured to a malicious website crafted by the attacker.

Once the victim visits the malicious site, the attacker can exploit the code injection vulnerability to execute commands with the privileges of the FortiClientMac application. This network-based attack requires no prior authentication, making it accessible to remote threat actors who can successfully social-engineer their targets.

Root Cause

The root cause of CVE-2025-31365 is improper validation and sanitization of code generation processes within FortiClientMac. The application fails to adequately control dynamically generated code, allowing externally influenced input to be incorporated into executable code paths. This lack of proper input validation in the code generation mechanism enables injection of malicious code that the application subsequently executes.

Attack Vector

The attack vector for this vulnerability is network-based and requires user interaction. An attacker must craft a malicious website containing exploit code targeting the FortiClientMac code injection flaw. When a user with a vulnerable FortiClientMac installation visits this website, the malicious code is injected and executed on their macOS system. The attack can potentially affect confidentiality, integrity, and availability of the compromised system, with the scope extending beyond the vulnerable component itself.

The vulnerability exploits the trust relationship between the user's browser session and the FortiClientMac application, leveraging improper code generation controls to achieve arbitrary code execution without requiring authentication.

Detection Methods for CVE-2025-31365

Indicators of Compromise

• Unexpected process spawning from FortiClientMac application with unusual command-line arguments
• Network connections from FortiClientMac to unknown or suspicious external IP addresses
• Anomalous file system activity in FortiClientMac application directories
• Suspicious JavaScript or web content execution correlated with FortiClientMac process activity

Detection Strategies

• Monitor FortiClientMac process behavior for code injection patterns and unexpected child processes
• Implement endpoint detection rules to identify anomalous code execution originating from FortiClientMac
• Deploy network monitoring to detect connections to known malicious domains or IPs when FortiClientMac is active
• Utilize behavioral analysis to detect deviations from normal FortiClientMac application patterns

Monitoring Recommendations

• Enable comprehensive logging for FortiClientMac application events on all macOS endpoints
• Implement real-time alerting for suspicious process chains involving FortiClientMac
• Monitor web traffic for indicators of exploitation attempts targeting FortiClientMac users
• Regularly review endpoint security logs for signs of post-exploitation activity

How to Mitigate CVE-2025-31365

Immediate Actions Required

• Update FortiClientMac to the latest patched version immediately
• Review all macOS endpoints for vulnerable FortiClientMac versions (7.4.0-7.4.3 and 7.2.1-7.2.8)
• Implement web filtering to block access to known malicious domains
• Educate users about the risks of visiting untrusted websites while FortiClientMac is running

Patch Information

Fortinet has released security updates to address CVE-2025-31365. Administrators should consult the Fortinet Security Advisory FG-IR-25-037 for detailed patch information and upgrade instructions. Organizations should prioritize upgrading FortiClientMac installations beyond the affected version ranges (7.4.0-7.4.3 and 7.2.1-7.2.8) to remediate this vulnerability.

Workarounds

• Restrict user web browsing on systems with vulnerable FortiClientMac versions until patches can be applied
• Implement network-level filtering to block access to suspicious or uncategorized websites
• Consider temporarily disabling FortiClientMac on critical systems if immediate patching is not possible
• Deploy additional endpoint protection controls to detect and block code injection attempts

# Verify FortiClientMac version on macOS
/Applications/FortiClient.app/Contents/MacOS/FortiClient --version

# Check for vulnerable versions and plan upgrade accordingly
# Consult Fortinet advisory FG-IR-25-037 for specific upgrade paths