Zero-Day Alert: Securing Your Perimeter Against the CVE-2026-24858 FortiCloud SSO Bypass
Security Alert: LevelUP Solutions Mitigation for CVE-2026-24858 Fortinet has disclosed a critical Authentication Bypass (CVE-2026-24858) affecting FortiOS and FortiManager, allowing attackers to gain full administrative control via the FortiCloud SSO path. At LevelUP Solutions, we are taking immediate action to shield our customers. Our MaintenanceUP team is currently deploying verified firmware patches (FortiOS 7.4.11+) and applying CLI-level hardening to disable vulnerable SSO entry points. Simultaneously, our MonitorUP service is conducting forensic log audits to ensure no "sleeper" admin accounts were created prior to the advisory. Is your perimeter secure? Reach out to the LevelUP Support Desk today for a complimentary firmware audit and risk assessment.
Another month, another critical Fortinet advisory. If you feel like you’re experiencing deja vu, you aren't alone. Hot on the heels of recent SSO vulnerabilities, Fortinet has disclosed CVE-2026-24858, a critical-severity authentication bypass vulnerability that is currently being exploited in the wild.
This isn't just a theoretical risk—CISA has already added it to its Known Exploited Vulnerabilities (KEV) catalog. At LevelUP Solutions, we are moving rapidly to ensure our customers are shielded from this threat. Here is the technical breakdown and how we are handling the heavy lifting for you.
The Technical Breakdown: What is CVE-2026-24858?
The vulnerability is classified as an Authentication Bypass Using an Alternate Path or Channel (CWE-288). It carries a critical CVSS score of 9.8.
In plain English: an attacker who has their own FortiCloud account and at least one registered Fortinet device can essentially "hop" over to other people's devices. If the target device has FortiCloud Single Sign-On (SSO) enabled, the attacker can log in with full administrative privileges without needing the target’s credentials.
Why is this happening?
While FortiCloud SSO is disabled by default in factory settings, it is often automatically enabled when an administrator registers a device through the GUI. Unless the "Allow administrative login using FortiCloud SSO" toggle is manually switched off, the "back door" is effectively left unlocked.
How LevelUP Solutions Protects Your Business
As your managed security partner, we take a multi-layered approach to zero-day vulnerabilities. We don't just wait for the next update; we proactively harden your environment.
1. Proactive Patch Management (MaintenanceUP)
Under our MaintenanceUP and Complete Package tiers, our engineers are already identifying all impacted FortiOS, FortiManager, and FortiAnalyzer units in your inventory.
Verified Deployment: We schedule emergency maintenance windows to deploy the latest firmware (e.g., FortiOS 7.4.11+) only after verifying it won't disrupt your specific VPN tunnels or routing.
Version Auditing: We identify "unsupported upgrade hops" to ensure your hardware remains stable during the transition.
2. Immediate Threat Containment & Hardening
For customers requiring high uptime, we implement immediate "Virtual Patching":
CLI Hardening: We manually audit and disable the "Allow administrative login using FortiCloud SSO" setting via the command line to close the specific attack vector without requiring a reboot.
ACL Restrictions: We ensure management interfaces are restricted to trusted LevelUP management IPs or secure "Jump Boxes," preventing public-facing exposure.
3. Deep Forensic Auditing (MonitorUP)
The biggest risk is that attackers may have already gained access to create "sleeper" admin accounts. Our MonitorUP service performs a deep dive:
Log Scrubbing: We scan your logs for unauthorized configuration downloads or logins from suspicious Cloudflare-fronted IPs (e.g.,
104.28.244.115).Persistence Checks: Our team performs a "clean-slate" audit of all local administrative accounts to ensure no backdoors like
auditorsvcadminhave been created.
Remediation Roadmap
| Phase | LevelUP Action | Customer Benefit |
| Identification | Inventory audit of all Fortinet assets. | Full visibility of your risk profile. |
| Mitigation | Disabling vulnerable SSO features via CLI. | Immediate reduction of the attack surface. |
| Remediation | Verified firmware upgrades to patched versions. | Permanent closure of the security hole. |
| Recovery | Credential rotation and integrity checks. | Certainty that no persistent threats remain. |
Final Thoughts
This vulnerability highlights the "double-edged sword" of cloud-integrated management. While SSO makes life easier, it creates a unified attack surface. By partnering with LevelUP Solutions, you ensure that your security fabric is managed with 24/7 vigilance.
Note: Fortinet has temporarily restricted SSO for unpatched devices. If you find you cannot log in via FortiCloud, please contact our support desk immediately for local access assistance.