Fortinet Patches Critical Authentication Bypass in FortiWeb Allowing Login with Random Credentials

Fortinet has released security updates addressing multiple vulnerabilities across FortiWeb, FortiManager, and FortiClient products. The most severe issue, tracked as CVE-2026-26035, affects FortiWeb and carries a CVSS score of 8.8. The flaw occurs when administrative accounts configured with remote RADIUS authentication use the wildcard option, which is disabled by default. Under these conditions, an unauthenticated remote attacker can gain administrative access to the web application firewall by supplying arbitrary usernames and passwords. Successful exploitation grants full control over the FortiWeb instance, potentially compromising web application security. The vulnerability impacts FortiWeb versions 8.0, 7.6, 7.4, 7.2, and 7.0, with fixes available in versions 8.0.3, 7.6.7, 7.4.12, and 7.2.13. No active exploitation of the authentication bypass flaws has been observed so far, but the risk of remote administrative access makes immediate patching essential for exposed appliances.

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Fortinet has issued patches for several vulnerabilities affecting its FortiWeb, FortiManager, and FortiClient products. The updates address flaws that could enable unauthorized administrative access without valid credentials and allow code execution on Windows systems.

The primary vulnerability, identified as CVE-2026-26035, impacts FortiWeb and received a CVSS score of 8.8. It manifests when administrative accounts using remote RADIUS authentication are configured with the wildcard option, a setting that is not enabled by default. In this scenario, a remote unauthenticated attacker can bypass authentication entirely and access either the graphical user interface or the command-line interface by entering any random username and password combination.

Once authenticated, the attacker obtains full administrative privileges over the web application firewall, allowing complete control of security policies and traffic inspection rules. The flaw affects multiple FortiWeb release lines, specifically versions 8.0, 7.6, 7.4, 7.2, and 7.0. Fixed releases are now available: 8.0.3, 7.6.7, 7.4.12, and 7.2.13.

At the time of disclosure, there were no indications of active exploitation targeting the authentication bypass issues. Nevertheless, the potential for unauthenticated remote administrative access makes prompt updates a high priority for any exposed FortiWeb appliances that protect critical network segments.

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