CVE-2025-32756: Fortinet FortiMail RCE Vulnerability

CVE-2025-32756 Overview

A stack-based buffer overflow vulnerability [CWE-121] in Fortinet FortiVoice versions 7.2.0, 7.0.0 through 7.0.6, 6.4.0 through 6.4.10, FortiRecorder versions 7.2.0 through 7.2.3, 7.0.0 through 7.0.5, 6.4.0 through 6.4.5, FortiMail versions 7.6.0 through 7.6.2, 7.4.0 through 7.4.4, 7.2.0 through 7.2.7, 7.0.0 through 7.0.8, FortiNDR versions 7.6.0, 7.4.0 through 7.4.7, 7.2.0 through 7.2.4, 7.0.0 through 7.0.6, FortiCamera versions 2.1.0 through 2.1.3, 2.0 all versions, 1.1 all versions, allows a remote unauthenticated attacker to execute arbitrary code or commands via sending HTTP requests with specially crafted hash cookie.

Critical Impact

This vulnerability allows remote code execution and could lead to full system compromise.

Affected Products

• Fortinet FortiMail
• Fortinet FortiNDR
• Fortinet FortiRecorder

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to Fortinet
• Not Available - CVE CVE-2025-32756 assigned
• Not Available - Fortinet releases security patch
• 2025-05-13 - CVE CVE-2025-32756 published to NVD
• 2025-10-24 - Last updated in NVD database

Technical Details for CVE-2025-32756

Vulnerability Analysis

The vulnerability stems from improper handling of input data, leading to a stack-based buffer overflow. This is exploited by sending a specially crafted HTTP request using a hash cookie to overflow the buffer and execute arbitrary code.

Root Cause

The root cause is a failure to validate the size of the input data against the buffer size, resulting in an overflow condition.

Attack Vector

The attack vector for this vulnerability is through network exposure, particularly via HTTP requests sent to affected Fortinet products.

// Potential exploitation code
#include <stdio.h>
#include <string.h>

void vulnerable_function(char *input) {
    char buffer[1024];
    strcpy(buffer, input); // No bounds checking
}

int main(int argc, char *argv[]) {
    if (argc < 2) return 1;
    vulnerable_function(argv[1]);
    return 0;
}

Detection Methods for CVE-2025-32756

Indicators of Compromise

• Unusual outbound network traffic
• Presence of unknown or suspicious processes
• Signs of unauthorized configuration modifications

Detection Strategies

Network traffic analysis can reveal abnormal patterns indicative of exploitation attempts. Endpoint monitoring for unexpected process executions or changes to system configurations is recommended.

Monitoring Recommendations

Implement network monitoring for irregular HTTP request patterns to affected products and deploy EDR solutions to identify potentially malicious code execution.

How to Mitigate CVE-2025-32756

Immediate Actions Required

• Block known malicious IP addresses
• Monitor for network anomalies
• Update to latest patched versions of all affected products

Patch Information

Please refer to the vendor advisory for the latest patch information and deployment guidelines.

Workarounds

If patching is not immediately possible, consider implementing strict network access controls to minimize exposure.

# Example firewall configuration
iptables -A INPUT -p tcp --dport 80 -s <trusted_ip> -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP