PSIRTOut-of-bounds Write in captive portal
Summary
An out-of-bounds write vulnerability [CWE-787] and a Stack-based Buffer Overflow [CWE-121] in FortiOS & FortiProxy captive portal may allow an inside attacker who has access to captive portal to execute arbitrary code or commands via specially crafted HTTP requests.
Workaround:
Set a non form-based authentication scheme:
config authentication scheme
edit scheme
set method method
next
end
Where <method> can be any of those :
ntlm NTLM authentication.
basic Basic HTTP authentication.
digest Digest HTTP authentication.
negotiate Negotiate authentication.
fsso Fortinet Single Sign-On (FSSO) authentication.
rsso RADIUS Single Sign-On (RSSO) authentication.
ssh-publickey Public key based SSH authentication.
cert Client certificate authentication.
saml SAML authentication
None of the enabled authentication schemes should be form-based.
Please note that only devices with captive portal enabled are affected.
| Version | Affected | Solution |
|---|---|---|
| FortiOS 7.4 | 7.4.0 through 7.4.1 | Upgrade to 7.4.2 or above |
| FortiOS 7.2 | 7.2.0 through 7.2.5 | Upgrade to 7.2.6 or above |
| FortiOS 7.0 | 7.0.0 through 7.0.12 | Upgrade to 7.0.13 or above |
| FortiOS 6.4 | 6.4.0 through 6.4.14 | Upgrade to 6.4.15 or above |
| FortiOS 6.2 | 6.2.0 through 6.2.15 | Upgrade to 6.2.16 or above |
| FortiProxy 7.4 | 7.4.0 | Upgrade to 7.4.1 or above |
| FortiProxy 7.2 | 7.2.0 through 7.2.6 | Upgrade to 7.2.7 or above |
| FortiProxy 7.0 | 7.0.0 through 7.0.12 | Upgrade to 7.0.13 or above |
| FortiProxy 2.0 | 2.0.0 through 2.0.13 | Upgrade to 2.0.14 or above |
| FortiProxy 1.2 | Not affected | Not Applicable |
| FortiSASE 23.3 | Not affected | Not Applicable |
| FortiSASE 23.2 | 23.2.b | Migrate to a fixed release |
| FortiSASE 23.1 | Not affected | Not Applicable |
| FortiSASE 22.4 | Not affected | Not Applicable |
Virtual Patch named "FortiOS.Captive.Portal.Out.Of.Bounds.Write." is available in FMWP db update 23.105
Acknowledgement
Internally discovered and reported by Gwendal Guégniaud of Fortinet Product Security Team.Timeline
2024-02-27: Initial publication2025-01-24: Move to Advisory table display