CVE-2026-25689: Fortinet FortiDeceptor RCE Vulnerability

CVE-2026-25689 Overview

An improper neutralization of argument delimiters in a command (argument injection) vulnerability has been identified in Fortinet FortiDeceptor. This security flaw allows a privileged attacker with super-admin profile and CLI access to delete sensitive files via crafted HTTP requests. The vulnerability affects multiple versions of FortiDeceptor, spanning from version 4.0 through version 6.2.0.

Critical Impact

A privileged attacker with super-admin access can exploit this argument injection vulnerability to delete sensitive files on FortiDeceptor systems, potentially leading to data loss, system instability, or compromise of deception infrastructure integrity.

Affected Products

• FortiDeceptor 6.2.0
• FortiDeceptor 6.0 all versions
• FortiDeceptor 5.3 all versions
• FortiDeceptor 5.2 all versions
• FortiDeceptor 5.1 all versions
• FortiDeceptor 5.0 all versions
• FortiDeceptor 4.3 all versions
• FortiDeceptor 4.2 all versions
• FortiDeceptor 4.1 all versions
• FortiDeceptor 4.0 all versions

Discovery Timeline

• 2026-03-10 - CVE-2026-25689 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-25689

Vulnerability Analysis

This vulnerability is classified as CWE-88 (Improper Neutralization of Argument Delimiters in a Command), commonly known as argument injection. The flaw exists in how FortiDeceptor processes command arguments, failing to properly sanitize or neutralize delimiter characters before passing user-controlled input to system commands.

The attack requires network access and high privileges (super-admin profile with CLI access), which limits the attack surface but presents a significant risk in scenarios where administrative credentials are compromised or where insider threats exist. Successful exploitation allows an attacker to manipulate command execution by injecting additional arguments, ultimately enabling the deletion of sensitive files on the target system.

Root Cause

The root cause stems from inadequate input validation and sanitization in FortiDeceptor's command processing logic. When handling HTTP requests, the application fails to properly neutralize argument delimiters, allowing specially crafted input to modify the intended command structure. This enables an attacker to inject malicious arguments that are then executed with the privileges of the application.

Attack Vector

The attack is executed remotely over the network through crafted HTTP requests. An attacker with super-admin profile access and CLI privileges can construct malicious HTTP requests containing argument injection payloads. These payloads exploit the improper neutralization of argument delimiters to execute unintended commands, specifically targeting file deletion operations.

The vulnerability manifests through insufficient validation of user-supplied arguments in HTTP request handlers. When these arguments are passed to internal commands without proper sanitization, delimiter characters (such as spaces, hyphens, or special characters) can be interpreted as argument separators, allowing injection of additional command parameters. Refer to the Fortinet Security Advisory FG-IR-26-094 for additional technical details.

Detection Methods for CVE-2026-25689

Indicators of Compromise

• Unexpected file deletions in FortiDeceptor system directories or configuration folders
• Anomalous HTTP requests to FortiDeceptor management interfaces containing unusual argument patterns or delimiter characters
• Audit log entries showing file operations initiated by super-admin accounts that deviate from normal administrative activities
• System instability or missing critical files following administrative HTTP activity

Detection Strategies

• Monitor FortiDeceptor access logs for HTTP requests containing suspicious argument patterns, escape characters, or delimiter sequences
• Implement file integrity monitoring (FIM) on critical FortiDeceptor system directories to detect unauthorized file deletions
• Configure SIEM rules to alert on unusual administrative activity patterns, particularly bulk file operations from super-admin accounts
• Deploy network traffic analysis to identify anomalous HTTP request payloads targeting FortiDeceptor management endpoints

Monitoring Recommendations

• Enable comprehensive audit logging for all FortiDeceptor administrative actions and file system operations
• Implement real-time alerting for file deletion events on FortiDeceptor systems, especially in critical directories
• Review super-admin account activity regularly for signs of abuse or compromised credentials
• Correlate FortiDeceptor logs with other security infrastructure to identify lateral movement or credential theft

How to Mitigate CVE-2026-25689

Immediate Actions Required

• Review and audit all super-admin accounts on FortiDeceptor systems to ensure they are legitimate and properly secured
• Restrict CLI access to only essential personnel and implement strict access controls
• Monitor FortiDeceptor systems for signs of exploitation or unauthorized file modifications
• Apply network segmentation to limit access to FortiDeceptor management interfaces from trusted networks only

Patch Information

Fortinet has released a security advisory addressing this vulnerability. Organizations should consult the Fortinet Security Advisory FG-IR-26-094 for specific patch information and upgrade guidance. It is recommended to upgrade FortiDeceptor to the latest patched version as specified in the vendor advisory.

Workarounds

• Implement strict network access controls to limit HTTP access to FortiDeceptor management interfaces
• Enforce multi-factor authentication (MFA) for all super-admin accounts to reduce the risk of credential compromise
• Deploy web application firewalls (WAF) to inspect and filter HTTP requests for argument injection patterns
• Regularly backup critical FortiDeceptor configurations and files to enable rapid recovery in case of exploitation

# Network access restriction example (firewall rules)
# Restrict FortiDeceptor management access to trusted admin networks only
# Example: Allow management access only from internal admin VLAN (10.10.10.0/24)
iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP