CVE-2023-25610: Fortinet FortiWeb RCE Vulnerability

CVE-2023-25610 Overview

CVE-2023-25610 is a critical buffer underwrite (buffer underflow) vulnerability affecting the administrative interface of multiple Fortinet products including FortiOS, FortiProxy, and FortiOS-6K7K. This memory corruption flaw allows remote unauthenticated attackers to execute arbitrary code or commands via specifically crafted requests targeting the vulnerable administrative interface.

Buffer underwrite vulnerabilities occur when a program writes data before the beginning of an allocated memory buffer, potentially corrupting adjacent memory regions and enabling attackers to hijack program execution flow. In the context of network security appliances like FortiGate firewalls, such vulnerabilities are particularly dangerous as they can provide attackers with complete control over perimeter security infrastructure.

Critical Impact

Remote unauthenticated attackers can achieve arbitrary code execution on affected Fortinet devices, potentially compromising entire network perimeters without requiring any credentials.

Affected Products

• Fortinet FortiOS version 7.2.0 through 7.2.3, 7.0.0 through 7.0.6, 6.4.0 through 6.4.11, and 6.2.12 and below
• Fortinet FortiProxy version 7.2.0 through 7.2.2, 7.0.0 through 7.0.8, and 2.0.12 and below
• Fortinet FortiOS-6K7K version 7.0.5, 6.4.0 through 6.4.10, and 6.2.0 through 6.2.10 and below
• Fortinet FortiWeb (multiple versions affected)
• Fortinet FortiSwitchManager (multiple versions affected)
• Fortinet FortiSwitch (multiple versions affected)
• Fortinet FortiManager (multiple versions affected)
• Fortinet FortiAnalyzer (multiple versions affected)

Discovery Timeline

• 2025-03-24 - CVE-2023-25610 published to NVD
• 2025-07-24 - Last updated in NVD database

Technical Details for CVE-2023-25610

Vulnerability Analysis

This vulnerability is classified as CWE-124 (Buffer Underwrite), a memory corruption vulnerability that occurs when a program writes data before the beginning of the intended buffer. Unlike buffer overflows which write beyond the end of a buffer, buffer underwrites corrupt memory regions that precede the allocated buffer space.

The vulnerability exists in the administrative interface of affected Fortinet products, which handles HTTP/HTTPS requests for device management. When processing specially crafted requests, the vulnerable code fails to properly validate input boundaries, allowing attackers to write data to memory locations before the start of allocated buffers.

Since the attack requires no authentication and is network-accessible, threat actors can target any internet-exposed Fortinet administrative interface. Successful exploitation can result in complete device compromise, including the ability to execute arbitrary code with the privileges of the affected service.

Root Cause

The root cause of CVE-2023-25610 is improper bounds checking in the administrative interface code when processing user-supplied input. The vulnerable code path allows negative index calculations or pointer arithmetic errors that result in writes to memory locations preceding the intended buffer allocation.

This type of vulnerability typically arises when:

• Array indices are calculated using user-controlled values without proper validation
• Pointer arithmetic operations fail to account for negative offsets
• Size calculations wrap around due to integer manipulation issues

The administrative interface's failure to validate input boundaries before memory operations creates the condition for buffer underwrite attacks.

Attack Vector

The attack vector for CVE-2023-25610 is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by:

1. Identifying an exposed Fortinet administrative interface (typically HTTPS on port 443 or custom management ports)
2. Crafting malicious HTTP/HTTPS requests with specially formatted payloads
3. Sending the crafted requests to trigger the buffer underwrite condition
4. Achieving arbitrary code execution through memory corruption

The attack complexity is low as exploitation can be achieved through standard HTTP/HTTPS requests. Organizations exposing administrative interfaces to untrusted networks are at immediate risk.

Detection Methods for CVE-2023-25610

Indicators of Compromise

• Unexpected crashes or restarts of Fortinet administrative services
• Anomalous HTTP/HTTPS traffic patterns targeting administrative interfaces
• Suspicious processes or connections originating from Fortinet devices
• Unauthorized configuration changes or new administrative accounts

Detection Strategies

• Monitor administrative interface access logs for unusual request patterns or malformed requests
• Implement network intrusion detection rules to identify exploitation attempts targeting the administrative web interface
• Enable and review FortiOS system event logs for process crashes and memory errors
• Deploy SentinelOne Singularity for network device monitoring and behavioral analysis of traffic to Fortinet infrastructure

Monitoring Recommendations

• Configure alerts for administrative interface access from unexpected source IP addresses
• Monitor for high-frequency or automated requests to management endpoints
• Track outbound connections from Fortinet devices to detect potential command and control activity
• Implement log aggregation and correlation for all Fortinet management plane activity

How to Mitigate CVE-2023-25610

Immediate Actions Required

• Restrict administrative interface access to trusted IP addresses only using local-in policies
• Disable HTTP/HTTPS administrative access from WAN interfaces immediately
• Apply vendor patches as soon as possible following the FortiGuard Security Advisory
• Audit current administrative interface exposure using external scanning tools

Patch Information

Fortinet has released security updates to address CVE-2023-25610 across affected product lines. Organizations should upgrade to the patched versions specified in the FortiGuard Security Advisory FG-IR-23-001. The advisory provides detailed version information and upgrade paths for all affected products including FortiOS, FortiProxy, FortiOS-6K7K, FortiWeb, FortiSwitchManager, FortiSwitch, FortiManager, and FortiAnalyzer.

Given the critical severity and network-based attack vector, patching should be treated as an emergency priority, especially for any devices with internet-exposed administrative interfaces.

Workarounds

• Disable administrative interface access from untrusted networks using config system interface and set allowaccess commands
• Implement local-in policies to restrict management access to specific trusted source IPs only
• Use a dedicated out-of-band management network isolated from production traffic
• Deploy a jump server or VPN requirement for all administrative access to Fortinet devices

# Configuration example - Restrict administrative access to trusted IPs
config firewall local-in-policy
    edit 1
        set intf "wan1"
        set srcaddr "trusted-admin-hosts"
        set dstaddr "all"
        set action deny
        set service HTTPS HTTP SSH
        set schedule "always"
        set status enable
    next
end