Detect Fortinet Multiple Products Authentication Bypass via Alternate Path or Channel (CVE-2026-24858) in Sumo Logic CSE
Detects exploitation of CVE-2026-24858, an authentication bypass vulnerability (CWE-288) affecting multiple Fortinet products. Attackers abuse an alternate authentication path or channel — specifically SSO abuse on FortiOS — to bypass normal authentication controls and gain unauthorized access. This vulnerability is listed on CISA's Known Exploited Vulnerabilities catalog, indicating active exploitation in the wild.
MITRE ATT&CK
Sumo Detection Query
_sourceCategory=fortinet OR _sourceCategory=fortigate OR _sourceName=*forti*
| where vendor matches /(?i)fortinet/ or _raw matches /(?i)(fortigate|fortios|forticlient)/
| where _raw matches /(?i)(sso|saml|alternate.path|auth.bypass|unauthenticated|bypass.auth)/
| parse "action=*" as action nodrop
| parse "srcip=*" as src_ip nodrop
| parse "dstip=*" as dst_ip nodrop
| parse "user=*" as username nodrop
| parse "msg=*" as message nodrop
| where action matches /(?i)(accept|allow|login|success|permit)/ or isNull(action)
| count as event_count by src_ip, username, action, _sourceHost
| where event_count >= 1
| sort by event_count desc
| fields _sourceHost, src_ip, username, action, event_countSumo Logic query for Fortinet authentication bypass detection, identifying successful authentication events referencing SSO, SAML, or alternate authentication channels on Fortinet devices.
Data Sources
Required Tables
False Positives & Tuning
- Standard SSO login flows from corporate identity providers
- Fortinet agent telemetry referencing SSO configuration in non-auth contexts
- Automated monitoring tools polling Fortinet management APIs with SSO tokens
- Multi-factor authentication bypass for break-glass accounts during incidents
Other platforms for CVE-2026-24858
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulate SSO Authentication Request to Fortinet Management Interface
Expected signal: HTTP request to /remote/logincheck with SSO/SAML parameters should appear in FortiGate authentication logs and in web proxy or network monitoring logs. Source IP, timestamp, and HTTP response code should be captured.
- Test 2Enumerate Fortinet Management Interface SSO Endpoints
Expected signal: Series of HTTPS connections to Fortinet management interface on TCP 443 from a single source IP targeting multiple URL paths in rapid succession. Should appear in web access logs and network flow data.
- Test 3Create Unauthorized Admin Account Post-Authentication-Bypass
Expected signal: FortiOS admin audit log should record a new admin account creation event with the account name 'svc_backup_acct', profile 'super_admin', and the API source IP. Event type=event, subtype=system, action=add should appear in FortiAnalyzer.
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