Fortinet FortiWeb CVE-2025-59719

The target FortiWeb appliance must have FortiCloud SSO login enabled and its SAML assertion consumer endpoint must be network-reachable to the attacker - typically the administrative/management interface. Vulnerable versions are FortiWeb 8.0.0, 7.6.0-7.6.4, or 7.4.0-7.4.9 specifically. No authentication and no user interaction are required (PR:N, UI:N), and complexity is low (AC:L), meaning the attacker only needs the ability to send a crafted SAML response to the endpoint. The principal limiting factor is configuration: deployments using only local admin authentication, or those where the management plane is firewalled off from untrusted networks, are not exploitable from the internet even if running a vulnerable build.

The CVSS 9.8 score (AV:N/AC:L/PR:N/UI:N) reflects network-reachable, unauthenticated, low-complexity exploitation yielding full confidentiality, integrity, and availability impact - a worst-case theoretical profile. However, EPSS is only 0.26% (50th percentile), suggesting limited current exploitation interest, and the CVE is not in CISA KEV at time of analysis. The signals are partially conflicting: the technical profile is severe, but exploitation requires that the target FortiWeb instance actually have FortiCloud SSO configured and exposed, which narrows the attackable population. Given Fortinet's history of being targeted by ransomware affiliates and nation-state actors (multiple prior FortiWeb/FortiOS CVEs in KEV), this should be treated as a high-priority patch despite the modest EPSS - the score likely reflects pre-disclosure conditions rather than long-term risk.

An attacker reachable over the network to a FortiWeb management interface with FortiCloud SSO enabled crafts a malicious SAML response - for example, by injecting an assertion for an administrative user and exploiting the broken signature verification (e.g., via XML signature wrapping or omission of a required signature element). The response is delivered to the SSO assertion consumer endpoint, the appliance accepts the forged assertion as valid, and the attacker obtains an authenticated admin session without credentials. No public exploit identified at time of analysis, but signature-verification flaws of this class historically have proof-of-concept code published shortly after disclosure.