Fortinet Multiple Products Authentication Bypass Using an Alternate Path or Channel Vulnerability
CVE-2026-24858 is a security vulnerability in Fortinet Multiple Products, added to CISA KEV on January 27, 2026. Patch priority: Patch this week.
What it is
Fortinet FortiAnalyzer, FortiManager, FortiOS, and FortiProxy contain an authentication bypass using an alternate path or channel that could 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.
Who's affected
Affects anyone whose internet connection goes through a Fortinet appliance — typically a FortiGate firewall or FortiClient VPN. The firewall sits between every device in the office and the internet; exploitation can mean an attacker gets inside the network perimeter without touching a workstation.
What to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Book a free 20-minute triage call.
Insurance readiness
Your insurer will ask if this is patched.
Unpatched entries on CISA's Known Exploited Vulnerabilities list are exactly what cyber-insurance carrier questionnaires probe for, and knowing which controls they check is how you keep a renewal from stalling.
Get the free carrier questionnaire →Severity
CVSS base score: 9.8 — CRITICAL
Weakness classification: CWE-288
CISA due date
Federal deadline: January 30, 2026. Federal agencies must complete the required action by this date. For private SMBs the deadline is advisory — but treat it as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
EPSS
EPSS score: 85.8% — higher than 100% of all scored CVEs.
EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.
Other exploited Fortinet Multiple Products entries
More CISA KEV entries for Fortinet Multiple Products. Same product line, same actively-exploited status.
Source
This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.