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Fortinet has patched an SSRF vulnerability in FortiSandbox that could let attackers proxy internal traffic via crafted HTTP requests.
Although Fortinet rated the issue as low severity, the flaw impacts a security appliance often deployed in segmented environments, which could make it a useful pivot if administrative access is ever compromised.
The vulnerability “… may allow an authenticated attacker to proxy internal requests limited to plaintext endpoints only via crafted HTTP requests,” said Fortinet in its advisory.
Inside CVE-2025-67685
CVE-2025-67685 is a server-side request forgery (SSRF) vulnerability tied to weak input validation and access controls in FortiSandbox’s GUI console.
Put simply, an authenticated attacker can submit specially crafted requests that make the appliance send network traffic on their behalf, effectively using FortiSandbox as a proxy to reach internal systems the attacker may not otherwise be able to access directly.
The behavior is limited to internal destinations — such as localhost and private IP ranges — and only supports connections to plaintext web services over HTTP/HTTPS without TLS.
That reduces the overall scope compared to broader SSRF issues that can reach arbitrary internet targets or sensitive cloud metadata endpoints.
Even with those constraints, the flaw can still be useful in real environments. Security appliances like FortiSandbox are often deployed deep inside segmented networks and routinely communicate with other internal services.
If an attacker gains valid credentials — particularly administrative access — SSRF can become a practical tool for internal discovery and pivoting. It may allow an attacker to:
- Enumerate internal services by testing hosts and ports that aren’t exposed externally.
- Retrieve internal responses such as banners, status pages, or basic API output.
- Interact with internal admin consoles that trust network location more than strong authentication.
- Support follow-on movement in environments where segmentation is a primary barrier.
In other words, the vulnerability isn’t necessarily a direct path to takeover, but it can give an attacker a helpful vantage point for reconnaissance and lateral movement within a restricted network.
Fortinet reports that there’s no evidence the vulnerability has been exploited in the wild.
Reducing SSRF Risk in Segmented Networks
Even low-severity SSRF vulnerabilities can carry outsized risk when they affect security appliances positioned deep within segmented networks.
FortiSandbox often operates with broad internal trust, meaning a compromised administrative account could be abused to proxy requests into sensitive services.
The mitigation steps below focus on reducing that risk by eliminating legacy exposure, hardening privileged access, and tightly constraining internal reach.
- Upgrade FortiSandbox versions and migrate off legacy 4.x branches to a fixed supported release.
- Restrict FortiSandbox GUI access to trusted management networks and isolate administration behind dedicated admin segments.
- Enforce strong privileged access controls by requiring MFA, using separate admin accounts, and limiting login sources and session duration.
- Apply strict egress controls so FortiSandbox can only reach approved internal endpoints and cannot proxy traffic across sensitive networks.
- Reduce SSRF reachable targets by disabling plaintext internal services where possible and migrating internal endpoints to TLS-only access.
- Audit GUI logs and deploy detections for SSRF-like behavior, including repeated localhost/internal IP fetches and unusual destination ports or request patterns.
- Test incident response playbooks for FortiSandbox compromise, including containment, log review, and credential rotation.
These steps help reduce FortiSandbox SSRF exposure by tightening access, limiting internal reach, and improving operational readiness.
Why This FortiSandbox Bug Still Matters
Fortinet’s fix reinforces an important security takeaway: even “low severity” flaws can matter when they affect trusted infrastructure sitting deep inside segmented networks.
Organizations using FortiSandbox should patch promptly to eliminate the proxying behavior.
They should also tighten privileged access, management-plane isolation, and outbound controls to limit internal reconnaissance or lateral movement if an account is compromised.
This kind of internal trust breakdown highlights why organizations are leveraging zero-trust, where access is continuously verified and segmentation alone isn’t treated as a primary security control.
