CVE-2026-24858 is an authentication bypass vulnerability (CWE-288) in Fortinet FortiWeb and other Fortinet products. It affects FortiWeb versions 7.4.0 through 7.4.11, 7.6.0 through 7.6.6, and 8.0.0 through 8.0.3. The vulnerability allows an attacker who possesses a FortiCloud account and a registered device to authenticate to devices registered to other accounts when FortiCloud Single Sign-On (SSO) authentication is enabled. This improper access control flaw enables unauthorized access across accounts. The vulnerability has a CVSS v3.1 base score of 9.4 (critical), reflecting network attack vector, low attack complexity, no privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. An official vendor fix is available.

Successful exploitation allows an attacker with a FortiCloud account and a registered device to bypass authentication controls and access devices registered to other accounts when FortiCloud SSO is enabled. This can lead to full compromise of affected devices, impacting confidentiality, integrity, and availability of the systems.

An official fix is available from Fortinet to address this vulnerability. Users should apply the vendor-provided patches promptly to affected FortiWeb versions and other impacted Fortinet products. Since the vulnerability requires FortiCloud SSO to be enabled, disabling this feature may mitigate risk temporarily if patching is not immediately possible.