The digital perimeter of modern organizations is under constant assault, and a single chink in the armor can expose vast internal networks to malicious actors. A recent disclosure by Fortinet has brought to light just such a vulnerability, shaking the confidence of many reliant on their FortiSandbox appliance. This critical flaw, a Server-Side Request Forgery (SSRF) vulnerability, presents a concerning avenue for attackers to proxy internal network traffic, potentially leading to unauthorized access and data exfiltration. Understanding the mechanics and implications of this vulnerability is paramount for any organization utilizing FortiSandbox.

Understanding the FortiSandbox SSRF Vulnerability: CVE-2025-67685

On January 13, 2026, Fortinet publicly disclosed a significant Server-Side Request Forgery (SSRF) vulnerability affecting its FortiSandbox appliance. Tracked officially as CVE-2025-67685 (and internally referenced as FG-IR-25-783), this flaw is not merely a theoretical concern but a serious security risk that demands immediate attention. The vulnerability’s root cause is classified under CWE-918, which denotes improper neutralization of special elements used in an OS command. Specifically, it resides within the graphical user interface (GUI) component of FortiSandbox.

The core danger of an SSRF vulnerability lies in its ability to coerce a server-side application to make HTTP requests to an arbitrary domain chosen by the attacker. In the context of FortiSandbox, this means an authenticated attacker can craft specific HTTP requests that force the appliance to act as a proxy. This allows the attacker to reach internal services and resources that are typically inaccessible from the external network. Imagine a scenario where an attacker, through this vulnerability, could make requests to internal administration panels, sensitive data stores, or other critical infrastructure typically protected by network segmentation.

The Mechanics of CWE-918 and Proxied Internal Traffic

CWE-918, a Server-Side Request Forgery vulnerability, occurs when a web application accepts a user-provided URL or part of a URL and then fetches data from that URL without proper validation. In the case of FortiSandbox, this allows an authenticated attacker to manipulate parameters within HTTP requests sent to the GUI. By cleverly constructing these requests, the attacker can specify internal IP addresses or hostnames that the FortiSandbox appliance will then attempt to access.

The result is the appliance making requests on behalf of the attacker to internal resources. This effectively bypasses network access controls and allows the attacker to:

• Scan internal networks: Identify active services, open ports, and operating system versions on internal hosts.
• Access internal services: Interact with web-based administration interfaces, APIs, or databases that are not exposed to the internet.
• Exfiltrate data: If internal services are vulnerable to other attacks, the SSRF can serve as a conduit to extract sensitive information.
• Bypass firewalls: Leverage the trusted position of the FortiSandbox appliance within the internal network to circumvent perimeter defenses.

The “plaintext” aspect mentioned in the source content suggests that the proxied traffic could potentially be unencrypted, further increasing the risk of data compromise if sensitive information is exchanged between internal services.

Who is at Risk?

Any organization utilizing Fortinet FortiSandbox appliances is potentially at risk, particularly those that have not yet applied the latest security patches. Since the vulnerability requires an authenticated attacker, initial access would typically involve compromised credentials or an internal threat actor. However, the severity escalates quickly once an attacker gains even limited authenticated access, as they can then leverage this SSRF flaw to expand their footprint significantly within the network.

Remediation Actions for FortiSandbox Users

Fortinet’s urgent advisory underscores the criticality of addressing CVE-2025-67685. The primary and most effective remediation is to update your FortiSandbox appliance immediately.

• Apply Patches: Refer to Fortinet’s official security advisory (FG-IR-25-783) for specific patch versions and instructions. Updating to the latest stable firmware release for your FortiSandbox model is crucial.
• Strengthen Authentication: Implement strong password policies and multi-factor authentication (MFA) for all administrative interfaces, including the FortiSandbox GUI, to minimize the risk of compromised credentials.
• Network Segmentation and Least Privilege: Review and reinforce network segmentation policies. Ensure that the FortiSandbox appliance only has necessary network access to perform its intended functions and is isolated from critical internal systems where possible.
• Monitor Logs: Implement robust logging and monitoring for the FortiSandbox appliance. Look for unusual outbound connections from the FortiSandbox to internal hosts that are not part of its normal operational behavior.
• Regular Security Audits: Conduct regular penetration testing and vulnerability assessments focused on internal network access from perimeter devices like sandboxes.

Tools for Detection and Mitigation

Tool Name	Purpose	Link
FortiSandbox Firmware Updates	Direct patch for CVE-2025-67685	Fortinet Support Downloads
Vulnerability Scanners (e.g., Nessus, Qualys)	Identify unpatched FortiSandbox instances and other network vulnerabilities.	Nessus Professional Qualys VMDR
Network Intrusion Detection/Prevention Systems (NIDS/NIPS)	Monitor for suspicious outbound connections and potential SSRF exploitation attempts.	Snort Suricata
Security Information and Event Management (SIEM)	Centralize logs from FortiSandbox and other devices for anomaly detection and forensics.	Splunk Elastic SIEM

Conclusion

The disclosure of CVE-2025-67685 in FortiSandbox serves as a stark reminder that even security appliances can harbor vulnerabilities that, if exploited, can undermine an organization’s entire security posture. The ability for an authenticated attacker to proxy internal network traffic is a serious concern, bypassing traditional perimeter defenses by leveraging a trusted internal device. Immediate action, primarily through patching and reinforcing network security practices, is essential to mitigate this risk and protect internal assets from potential compromise.