FORTINET CONFIRMS NEW ZERO-DAY BEHIND MALICIOUS SSO LOGINS

Summary from the TLDR InfoSec newsletter

CVE-2026-24858 is a critical authentication-bypass vulnerability (CVSS 9.8) that affects FortiOS, FortiManager, FortiAnalyzer, FortiProxy, and FortiWeb. It allows attackers to log in to devices via FortiCloud SSO. The zero-day, added to CISA's KEV catalog, emerged after reports that the December CVE-2025-59718 patch was being bypassed, prompting Fortinet to temporarily disable FortiCloud SSO globally on January 26. Organizations should immediately upgrade affected products. FortiCloud SSO now blocks login attempts from vulnerable device versions.