FORTINET: 🔰 Header Injection in Captive Portal Authentication Form

FORTINET Security Advisory

Published Date: July 14, 2026

Advisory Summary

Fortinet has identified a moderate-severity vulnerability (CVSSv3 Score: 3.1) in its FortiOS and FortiProxy captive portal systems. This issue, classified as Improper Neutralization of CRLF Sequences in HTTP Headers (CWE-113), commonly known as HTTP Response Splitting, allows an attacker with interception capabilities to inject arbitrary HTTP headers by manipulating the user’s authentication requests.

Such injection could lead to various attack vectors, including potential session fixation, web cache poisoning, or manipulation of HTTP responses, potentially impacting the integrity of captive portal authentication processes. While the vulnerability requires an ability to intercept and tamper with traffic, environments employing captive portals should prioritize patching to safeguard user authentication workflows.

IT infrastructure teams managing FortiOS or FortiProxy captive portals must review their security posture and apply Fortinet’s recommended patches or mitigations promptly to prevent exploitation.

• Verify and apply available patches from Fortinet immediately.
• Monitor authentication traffic for abnormal header modifications.
• Ensure secure transmission channels (e.g., HTTPS) to minimize interception risk.

Reference: Vendor Advisory