Security Advisory

CVE-2026-24858

About

An Authentication Bypass Using an Alternate Path or Channel vulnerability [CWE-288] vulnerability in Fortinet FortiAnalyzer 7.6.0 through 7.6.5, FortiAnalyzer 7.4.0 through 7.4.9, FortiAnalyzer 7.2.0 through 7.2.11, FortiAnalyzer 7.0.0 through 7.0.15, FortiManager 7.6.0 through 7.6.5, FortiManager 7.4.0 through 7.4.9, FortiManager 7.2.0 through 7.2.11, FortiManager 7.0.0 through 7.0.15, FortiNAC-F 7.6.3 through 7.6.5, FortiOS 7.6.0 through 7.6.5, FortiOS 7.4.0 through 7.4.10, FortiOS 7.2.0 through 7.2.12, FortiOS 7.0.0 through 7.0.18, FortiProxy 7.6.0 through 7.6.4, FortiProxy 7.4.0 through 7.4.12, FortiProxy 7.2.0 through 7.2.15, FortiProxy 7.0.0 through 7.0.22, FortiWeb 8.0.0 through 8.0.3, FortiWeb 7.6.0 through 7.6.6, FortiWeb 7.4.0 through 7.4.11 may allow an attacker with a FortiCloud account and a registered device to log into other devices registered to other accounts, if FortiCloud SSO authentication is enabled on those devices.

Weakness (CWE):CWE-288

Rainforest analyst review

This is an authentication bypass through an alternate channel affecting a broad swath of Fortinet's product line, including FortiOS, FortiProxy, FortiManager, FortiAnalyzer, FortiWeb, and FortiNAC-F. The flaw lives in the FortiCloud SSO login path: when a device has FortiCloud SSO enabled, an attacker who holds a FortiCloud account with a registered device of their own can use that legitimate footing to log into other devices registered to entirely different accounts. In effect the SSO channel fails to bind a device to its rightful owner, letting one tenant authenticate into another's equipment.

These are firewalls, proxies, and security-management appliances that sit at the network perimeter and hold the keys to policy and traffic across the organization, so unauthorized login is a direct route to controlling the defenses. Fortinet devices are a perennial target for both ransomware crews and state actors, and any SSO bypass across this many products draws fast attention. The precondition is that FortiCloud SSO is enabled on the exposed device, the first thing to check. Apply Fortinet's fixed firmware for each affected product, and where patching lags, disable FortiCloud SSO or restrict management access, then review login records for sessions that do not correspond to legitimate account owners.

References

Frequently asked questions

What is CVE-2026-24858?

How severe is CVE-2026-24858?

CVE-2026-24858 carries a CVSS 3.1 base score of 9.8, rated critical. On the Rainforest Risk Index — which weighs the severity alongside how easy the flaw is to reach and how broad its impact is — it scores 99 out of 100, in the critical band.

How is CVE-2026-24858 exploited?

According to the CVSS vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H): attack vector Network, attack complexity Low, privileges required None, user interaction None. Impact on confidentiality High, integrity High and availability High.

Which products are affected by CVE-2026-24858?

Public advisories list the following as affected: fortianalyzer, fortimanager, fortinac-f, fortios, fortiproxy, fortiweb, +2. Check the references on this page for the exact versions each vendor confirms.

How do I fix CVE-2026-24858?

Apply the fix the vendor published — the references on this page link to the primary advisories and patches. When patching can't happen right away, reduce the exposure of the affected component and watch it for exploitation attempts. Rainforest customers see this vulnerability correlated to their own assets and prioritized by real exposure, not by score alone.

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