PoC Released for Fortinet FortiSIEM Command Injection Flaw

Security researchers have uncovered a severe pre-authentication command injection vulnerability in Fortinet’s FortiSIEM platform that allows attackers to completely compromise enterprise security monitoring systems without any credentials.

The vulnerability, designated CVE-2025-25256, has already been exploited by attackers in real-world scenarios, raising urgent concerns about the security of critical infrastructure monitoring tools.

Enterprise Security Platform Hit by Critical Flaw

FortiSIEM, Fortinet’s flagship Security Information and Event Management (SIEM) solution, is widely deployed across enterprise environments to monitor security events, correlate threats, and provide automated incident response capabilities.

The platform is designed to be the central nervous system of corporate security operations centers (SOCs), making this vulnerability particularly concerning for organizations worldwide.

The flaw exists within the phMonitor component, a C++ binary that operates on port 7900 and is responsible for monitoring the health of FortiSIEM processes.

Researchers from watchTowr Labs discovered that the vulnerability stems from inadequate input sanitization in the handleStorageArchiveRequest function, where user-controlled XML data is processed without proper validation.

The vulnerability affects an extensive range of FortiSIEM versions:

• All versions from 5.4 through 7.3.1 are vulnerable to exploitation.
• Legacy versions dating back several years require complete migration to fixed releases.
• FortiSIEM 7.4 is not affected by this vulnerability.
• Patched versions include 7.3.2, 7.2.6, 7.1.8, 7.0.4, and 6.7.10.
• Versions 6.6 and earlier cannot be incrementally patched and require full migration.

This broad impact means that organizations running legacy versions are potentially at significant risk of compromise.

Real-World Attacks

Perhaps most alarming is Fortinet’s acknowledgment that “practical exploit code for this vulnerability was found in the wild”.

This revelation challenges the common narrative that vulnerabilities only become dangerous after security researchers publish detailed analysis.

Instead, it demonstrates that malicious actors are actively discovering and exploiting these flaws independently.

The technical analysis reveals that attackers can exploit this vulnerability by sending specially crafted XML payloads to the affected phMonitor service.

The malicious input bypasses the inadequate addParaSafe function, which only performed basic quote escaping rather than comprehensive input sanitization.

In vulnerable versions, this allows attackers to inject arbitrary commands that execute with the privileges of the FortiSIEM system.

Security teams should treat this vulnerability as a critical priority requiring immediate attention.

The fact that SIEM systems are specifically targeted makes this particularly dangerous, as compromising these platforms can blind organizations to ongoing attacks and potentially provide attackers with comprehensive visibility into network security posture.

Organizations should immediately inventory their FortiSIEM deployments and verify current version numbers against Fortinet’s advisory.

For versions 6.6 and earlier, Fortinet recommends complete migration to newer, patched releases rather than incremental updates.

WatchTowr Labs has released a Detection Artefact Generator to help security teams identify potential exploitation attempts in their environments.

Given the simplicity of the exploit and confirmed in-the-wild usage, organizations should assume active scanning and exploitation attempts are already occurring.

The incident underscores broader concerns about the security posture of security tools themselves, highlighting the critical importance of treating security infrastructure with the same rigorous protection standards applied to other critical business systems.

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