A critical security vulnerability in the Fortinet FortiSIEM platform allows unauthenticated attackers to execute arbitrary commands remotely.
The vulnerability CVE-2025-25256, classified as CWE-78 (OS Command Injection), has been actively exploited in the wild with practical exploit code already circulating among threat actors.
Key Takeaways
1. Critical FortiSIEM flaw actively exploited with PoC in the wild.
2. Targets phMonitor port 7900; no clear IoCs.
3. Upgrade to patched versions or migrate.
FortiSIEM Vulnerability
The vulnerability stems from improper neutralization of special elements used in operating system commands within FortiSIEM’s architecture.
Specifically, the flaw allows remote unauthenticated command injection through crafted Command Line Interface (CLI) requests targeting the system.
This represents a severe security risk as attackers can bypass authentication mechanisms entirely and execute unauthorized code or commands on vulnerable systems.
The exploit leverages the phMonitor port 7900, which serves as the primary attack vector for malicious actors.
Security researchers have confirmed that practical exploit code for this vulnerability was discovered in active use, indicating that threat actors are already weaponizing this flaw against real-world targets.
The exploitation code reportedly does not produce distinctive Indicators of Compromise (IoCs), making detection particularly challenging for security teams.
The vulnerability impacts multiple FortiSIEM versions across several major releases. Organizations running FortiSIEM versions 6.1 through 6.6 face the highest risk, as these versions require complete migration to fixed releases rather than simple upgrades.
| Risk Factors | Details |
| Affected Products | FortiSIEM 7.3.0–7.3.1, 7.2.0–7.2.5, 7.1.0–7.1.7, 7.0.0–7.0.3, 6.7.0–6.7.9, all versions of 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, and 5.4 |
| Impact | Arbitrary command execution |
| Exploit Prerequisites | Network access to the phMonitor service on port 7900; no authentication required |
| CVSS 3.1 Score | 9.8 (Critical) |
Patch Available
For newer versions, specific upgrade paths are available: FortiSIEM 7.3 users should upgrade to version 7.3.2 or above, while version 7.2 users need to update to 7.2.6 or higher.
Similarly, FortiSIEM 7.1 requires upgrading to 7.1.8 or above, and version 7.0 needs updating to 7.0.4 or newer.
FortiSIEM 6.7 users can upgrade to version 6.7.10 or above to address the vulnerability. Notably, FortiSIEM 7.4 remains unaffected by this security flaw.
As an immediate workaround, Fortinet recommends limiting access to the phMonitor port 7900 to reduce exposure until proper patches can be implemented.
The advisory was initially published on August 12, 2025, emphasizing the urgency for organizations to assess their FortiSIEM deployments and implement appropriate remediation measures immediately.
Given the active exploitation and availability of working exploit code, security teams should prioritize this vulnerability in their patching schedules.
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