CVE-2023-27997: Fortinet FortiProxy SSL-VPN RCE Vulnerability

CVE-2023-27997 Overview

A heap-based buffer overflow vulnerability [CWE-122] in FortiOS version 7.2.4 and below, version 7.0.11 and below, version 6.4.12 and below, version 6.0.16 and below and FortiProxy version 7.2.3 and below, version 7.0.9 and below, version 2.0.12 and below, version 1.2 all versions, version 1.1 all versions SSL-VPN may allow a remote attacker to execute arbitrary code or commands via specifically crafted requests.

Critical Impact
This vulnerability allows remote attackers to execute arbitrary code, potentially compromising system integrity.

Affected Products

Fortinet FortiProxy
Fortinet FortiOS
Fortinet FortiGate 6000

Discovery Timeline

2023-06-13 - CVE CVE-2023-27997 published to NVD
2025-10-24 - Last updated in NVD database

Technical Details for CVE-2023-27997

Vulnerability Analysis

The vulnerability stems from improper handling of user-supplied input within the SSL-VPN component. This allows attackers to trigger a buffer overflow, leading to arbitrary code execution.

Root Cause

The root cause of this vulnerability is the inadequate validation of input length before copying it into a buffer, resulting in a heap-based buffer overflow.

Attack Vector

This vulnerability can be exploited remotely via the network.

// Example exploitation code (sanitized)
#include <string.h>
void vulnerable_function(char *input) {
    char buffer[256];
    strcpy(buffer, input); // Vulnerable line
}

Detection Methods for CVE-2023-27997

Indicators of Compromise

Unusual traffic via SSL-VPN
Unexpected system reboots
Presence of unknown binaries

Detection Strategies

Network traffic analysis should focus on SSL-VPN usage patterns and unusual packet sizes. Endpoint monitoring can detect post-exploitation activities.

Monitoring Recommendations

Utilize network-based intrusion detection systems (IDS) to monitor for anomalies in SSL-VPN activities. Implement host-based intrusion detection for signs of privilege escalation or code execution.

How to Mitigate CVE-2023-27997

Immediate Actions Required

Disable vulnerable SSL-VPN features
Restrict network access to critical systems

Patch Information

Apply the latest security patches released by Fortinet as per their advisory.

Workarounds

As a temporary measure, disable the SSL-VPN service if not needed. Utilize firewall rules to restrict unauthorized access.

bash

# Configuration example
iptables -A INPUT -p tcp --dport 10443 -j DROP