Fortinet SSO Bypass Attacks: AI Response Playbook

A CVSS 9.1 bug is bad. A CVSS 9.1 bug that enables unauthenticated admin access on perimeter gear is a different category of problem—because the attacker isn’t chasing one server, they’re chasing your network choke points.

That’s exactly what’s happening with two critical Fortinet authentication bypass vulnerabilities (CVE-2025-59718 and CVE-2025-59719). The pattern reported so far is blunt and efficient: attackers bypass SSO authentication with crafted SAML messages (when FortiCloud SSO is enabled), sign in as admin, then export device configs—including hashed credentials and other sensitive details that can be reused for follow-on access.

This post is part of our AI in Cybersecurity series, and I’m going to be direct: most organizations are still treating perimeter-device exploitation like a “patch when we can” IT task. It’s not. It’s an incident-response problem with a vulnerability-management trigger—and it’s where AI-driven detection and automated response earn their keep.

What’s happening with the Fortinet flaws (and why it’s urgent)

Answer first: Attackers are actively exploiting Fortinet SSO authentication bypass bugs to gain admin access and steal configurations, and the window between disclosure and exploitation is measured in days.

Fortinet disclosed two critical authentication bypass flaws on December 9, 2025. Observed malicious activity began around December 12—roughly three days later. That timing matters because it mirrors what defenders have learned the hard way: once an exploit path is public, mass scanning and opportunistic compromise follow quickly, especially for internet-facing security appliances.

Here’s the core issue in plain language:

• The bypass targets SSO login authentication using SAML.
• It hinges on improper verification of cryptographic signatures in crafted messages.
• If FortiCloud SSO is enabled, an unauthenticated attacker can potentially obtain admin-level access.

If that sounds abstract, translate it like this: your firewall/VPN platform can become the attacker’s remote admin console—without stolen passwords.

The “gotcha” that likely expanded exposure

Answer first: More environments may be exposed than expected because FortiCloud SSO is disabled by default, but it can become enabled during device registration unless it’s explicitly toggled off.

A design detail matters here: FortiCloud SSO is disabled in factory defaults, but it may automatically activate when administrators register devices via the GUI using FortiCare, unless the admin turns off the “Allow administrative login using FortiCloud SSO” toggle.

That’s the kind of subtle setting drift that shows up constantly in incident reviews:

• A feature is “off by default.”
• A workflow turns it on.
• Nobody notices.
• Months later, it’s the entry point.

Why perimeter-device exploits hit harder than “normal” breaches

Answer first: Compromising a perimeter appliance can give attackers control over traffic routing, VPN access, and security policy—turning one bug into organization-wide access.

When attackers land on an endpoint, they still have to move. When they land on a firewall, VPN concentrator, or web proxy, they can often shape the battlefield.

Once authenticated as admin, the observed behavior includes exporting configuration data. That’s not random theft—it’s a blueprint:

• Network topology (interfaces, routes, VIPs, NAT rules)
• VPN configuration (portals, authentication methods, user groups)
• Security policies (what’s allowed, what’s logged, what’s ignored)
• Local users and hashed credentials

Hashed credentials are particularly dangerous because attackers can attempt offline cracking. If your admin password policy is weak or reused, the attacker can convert “I got a config export once” into “I have durable credentials for later.”

A line I’ve found useful when talking to leadership is:

If an attacker gets admin on perimeter infrastructure, you’re not defending a breach—you’re defending your ability to see and control the network.

Patch fast, but reduce exposure faster (the practical order of operations)

Answer first: The fastest risk reduction is limiting or removing internet-exposed management access and disabling vulnerable SSO paths, even before your maintenance window.

Patching Fortinet devices can require maintenance windows, testing, and change control. That’s real life. But “we patch next week” doesn’t help if your management interface is reachable right now.

A pragmatic sequence that works in the field:

1. Confirm exposure

   • Identify which Fortinet products/versions you run.
   • Verify whether FortiCloud SSO is enabled.
   • Confirm whether HTTP/HTTPS admin is reachable from the internet (or overly broad networks).

2. Apply immediate containment (same day)

   • Disable FortiCloud SSO administrative login if you can’t patch immediately.
   • Restrict administrative access to trusted IP ranges only.
   • Prefer a dedicated management network or VPN for admin access.
   • If possible, temporarily disable internet-facing admin interfaces.

3. Patch/upgrade to fixed versions (as soon as feasible)

   • Plan a short maintenance window.
   • Patch across HA pairs carefully (avoid asymmetric versions).
   • Verify that SSO settings didn’t revert or remain enabled unintentionally.

4. Assume credential exposure if suspicious activity exists

   • Reset firewall/admin credentials.
   • Rotate any secrets that might be stored or referenced in configs.
   • Review local admin accounts and API tokens.

That’s the human process. Now let’s talk about where AI fits in a way that’s actually useful.

Where AI-driven threat detection pays off in this exact scenario

Answer first: AI helps by spotting abnormal authentication, configuration export behavior, and post-compromise changes faster than rules alone—then triggering containment actions automatically.

These Fortinet attacks aren’t “stealth malware.” They’re abuse of legitimate admin capabilities after an authentication bypass. Traditional detections often miss that because the activity can look like normal admin work:

• Admin login succeeds.
• Config export occurs.
• Policy changes happen.

That’s why this is a strong real-world case for AI in cybersecurity: you need systems that understand behavioral baselines and can correlate weak signals across logs, identity, and network telemetry.

1) Detecting malicious SSO logins and impossible admin behavior

Answer first: AI models can flag admin logins that don’t match historical patterns, even when credentials appear valid.

Good anomaly detection isn’t magic—it’s disciplined baselining:

• Which admin accounts usually log in?
• From which IP ranges and geographies?
• At what times?
• With what user agents or management methods (GUI vs CLI)?

Then you alert on deviations that matter. Examples that should trip alarms:

• First-time admin login from a new ASN/hosting provider
• A “successful” SSO login followed immediately by config export
• Multiple devices accessed from one source in a short window
• Admin actions executed outside normal change windows

AI helps reduce false positives by learning what “weird but normal” looks like in your environment.

2) Catching config export and sensitive-object access as a high-signal event

Answer first: Treat configuration export as a high-risk action and let AI prioritize it when it follows unusual authentication.

Many teams log config exports but don’t alarm on them. They should.

A practical detection policy:

• High severity if config export occurs within 15 minutes of a new admin session from an unfamiliar source.
• Critical severity if the same source performs exports across multiple devices.
• Escalate automatically if the session also creates users, changes VPN settings, or alters logging.

This is where AI-assisted correlation matters: each event alone may look benign. Together, they’re an incident.

3) Automated response that buys time (and reduces blast radius)

Answer first: The right automation steps are boring, fast, and reversible—perfect for AI-orchestrated playbooks.

When you suspect perimeter compromise, speed matters more than elegance. Automated actions that are both effective and relatively safe:

• Temporarily restrict admin access to a known jump host IP range
• Disable FortiCloud SSO admin login pending validation
• Force step-up authentication for admin sessions (where supported)
• Snapshot configs and logs to secure storage for forensics
• Open an incident ticket with a pre-filled timeline of correlated events

The goal isn’t to “auto-remediate everything.” It’s to stop the bleeding and preserve evidence while humans validate.

A practical AI-assisted incident workflow for Fortinet exploitation

Answer first: Combine vulnerability signals (CVE exposure) with behavior signals (admin anomalies) so you don’t rely on either alone.

Here’s a workflow I like because it mirrors how attackers operate—fast, opportunistic, and repetitive.

Step 1: Exposure-driven prioritization

Start with what you can measure quickly:

• Internet-facing management interface? Highest priority.
• FortiCloud SSO enabled? Raise priority.
• Unpatched version in affected lines? Raise priority again.

AI can help here by continuously reconciling asset inventory, configuration state, and vulnerability advisories, then generating a ranked “patch first” queue.

Step 2: Behavior-driven confirmation

Now verify whether exploitation already happened:

• New admin sessions from unfamiliar IP space
• Evidence of configuration export
• New local admin accounts or changes to existing ones
• VPN config changes or new tunnels
• Unexpected drops in logging or changes to log destinations

A strong security analytics platform can score these events and surface the most likely compromised devices first.

Step 3: Contain and rotate

If your signals indicate compromise, treat it like compromise:

• Restrict management access immediately
• Rotate credentials and keys that could be derived from configs
• Patch to fixed versions
• Validate policies, VPN settings, and logging integrity

If you do only one thing: rotate credentials after suspicious config export. It’s the difference between “one scary day” and “persistent access for months.”

Questions security teams are asking this week (and direct answers)

“If we patched, are we done?”

Answer: Not necessarily. If attackers exported configs before you patched, you still have a credential and topology exposure problem. Review logs, rotate secrets, and validate config integrity.

“We don’t expose admin UI to the internet. Are we safe?”

Answer: You’re safer, but not invulnerable. Many environments still have broad access from third-party networks, remote admin tools, or misconfigured ACLs. Validate reachability externally, not just internally.

“Can AI really help, or is this just patch management?”

Answer: Patch management reduces the vulnerability. AI-driven detection reduces the time-to-detect and time-to-contain when exploitation starts before your change window. In real incidents, that gap is where damage happens.

What to do next (before the next appliance CVE drops)

Perimeter devices will keep being targeted because the payoff is enormous and the attack paths are repeatable. The Fortinet SSO bypass campaign is just the latest reminder.

If you’re building an AI in Cybersecurity program, this is a perfect place to start because the success criteria are clear:

• Can you identify exposed management surfaces in hours, not weeks?
• Can you detect anomalous admin behavior and config exports in minutes?
• Can you contain access automatically while preserving evidence?

If you want a concrete next step, run a tabletop exercise with one scenario: “Firewall admin access achieved; config exported.” Then decide what you’d automate on day one versus what you’d require human approval for.

The uncomfortable question to end on: if an attacker signed into your perimeter device as admin tonight, would your team know before morning—and would your systems react before the attacker comes back for round two?