CVE-2025-64155: Fortinet FortiSIEM RCE Vulnerability

CVE-2025-64155 Overview

CVE-2025-64155 is a critical OS command injection vulnerability affecting multiple versions of Fortinet FortiSIEM, a Security Information and Event Management (SIEM) solution. The vulnerability allows remote attackers to execute arbitrary operating system commands through specially crafted TCP requests without requiring authentication. This flaw stems from improper neutralization of special elements used in OS commands (CWE-78), enabling attackers to bypass security controls and gain unauthorized access to the underlying system.

Critical Impact

Unauthenticated remote attackers can execute arbitrary OS commands on vulnerable FortiSIEM systems via crafted TCP requests, potentially leading to complete system compromise, data exfiltration, and lateral movement within enterprise networks.

Affected Products

• Fortinet FortiSIEM 7.4.0
• Fortinet FortiSIEM 7.3.0 through 7.3.4
• Fortinet FortiSIEM 7.1.0 through 7.1.8
• Fortinet FortiSIEM 7.0.0 through 7.0.4
• Fortinet FortiSIEM 6.7.0 through 6.7.10

Discovery Timeline

• January 13, 2026 - CVE-2025-64155 published to NVD
• January 20, 2026 - Last updated in NVD database

Technical Details for CVE-2025-64155

Vulnerability Analysis

This vulnerability represents a severe security flaw in Fortinet FortiSIEM's TCP request handling mechanism. The affected component fails to properly sanitize user-supplied input before incorporating it into OS command execution contexts. As a network-accessible vulnerability requiring no privileges or user interaction, it presents an ideal attack surface for remote adversaries targeting enterprise SIEM infrastructure.

The exploitation path is particularly concerning as FortiSIEM deployments typically occupy privileged positions within enterprise networks, having access to security logs and sensitive operational data from across the organization. Successful exploitation could allow attackers to not only compromise the SIEM system itself but also leverage its network position and access to escalate attacks throughout the environment.

Root Cause

The root cause is improper neutralization of special elements used in OS commands (CWE-78). The FortiSIEM application fails to adequately validate and sanitize input data received through TCP connections before passing it to shell commands or system calls. This allows attackers to inject shell metacharacters or command separators that break out of the intended command context and execute arbitrary commands with the privileges of the FortiSIEM service account.

Attack Vector

The vulnerability is exploitable over the network through crafted TCP requests. An attacker can send malicious payloads containing OS command injection sequences to a vulnerable FortiSIEM instance. The attack requires no authentication and no user interaction, making it highly exploitable. The injected commands execute in the context of the FortiSIEM application, typically with elevated privileges.

Technical proof-of-concept resources have been published that demonstrate exploitation techniques. Security teams should reference the Horizon3 AI PoC repository and the CVE-2025-64155 Hunter tool for additional technical details on the attack methodology.

Detection Methods for CVE-2025-64155

Indicators of Compromise

• Unusual outbound network connections from FortiSIEM servers to external IP addresses
• Unexpected child processes spawned by FortiSIEM application services
• Suspicious command execution patterns in system logs including shell invocations with encoded or obfuscated parameters
• Creation of unauthorized user accounts or SSH keys on FortiSIEM systems
• Anomalous TCP traffic patterns or unexpected service ports active on FortiSIEM infrastructure

Detection Strategies

• Deploy network intrusion detection signatures targeting command injection patterns in TCP traffic destined for FortiSIEM ports
• Implement endpoint detection rules to alert on suspicious process chains originating from FortiSIEM binaries
• Monitor FortiSIEM system logs for evidence of command execution anomalies or error messages indicating injection attempts
• Correlate network flow data for unusual communication patterns from FortiSIEM servers

Monitoring Recommendations

• Enable comprehensive logging on FortiSIEM systems including system call auditing and network connection logging
• Configure SIEM rules to detect and alert on command injection attack patterns targeting FortiSIEM infrastructure
• Establish baseline behavior profiles for FortiSIEM servers to identify deviations indicative of compromise
• Implement network segmentation monitoring to detect unauthorized lateral movement from compromised SIEM systems

How to Mitigate CVE-2025-64155

Immediate Actions Required

• Identify all FortiSIEM deployments within the environment and verify version numbers against the affected range
• Apply vendor patches immediately following testing in a staging environment
• Restrict network access to FortiSIEM management interfaces using firewall rules and access control lists
• Implement network segmentation to isolate FortiSIEM systems from untrusted network segments
• Enable enhanced logging and monitoring on all FortiSIEM systems pending patch deployment

Patch Information

Fortinet has released security updates to address this vulnerability. Organizations should consult the Fortinet PSIRT Advisory FG-IR-25-772 for official patch information, updated firmware versions, and detailed remediation guidance. Apply the latest available security patches to all affected FortiSIEM versions immediately.

Workarounds

• Implement strict network access controls limiting TCP connections to FortiSIEM servers to authorized management hosts only
• Deploy a web application firewall (WAF) or network-based intrusion prevention system (IPS) with command injection detection capabilities in front of FortiSIEM infrastructure
• Consider temporarily isolating vulnerable FortiSIEM systems from direct network exposure until patches can be applied
• Enable additional authentication mechanisms or VPN requirements for accessing FortiSIEM management interfaces

# Example firewall rule to restrict FortiSIEM access (adjust ports as needed)
iptables -A INPUT -p tcp --dport 443 -s <trusted_management_subnet> -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP