Fortinet: Header injection in Web Filter warning page

Description

An Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability [CWE-113] in FortiOS and FortiProxy may allow an attacker in possession of a valid web filter override token to inject arbitrary headers via tricking a user into clicking on a crafted link. Revised on 2026-07-14 00:00:00

What to do

Install the fixed versions listed in the official advisory. If you cannot update right away, apply the workarounds or mitigations it describes and limit access to the affected service.

Details

Vendor

Fortinet

Product

FortiOS, FortiProxy

Affected versions

FortiOS 7.6: from 7.6.0 to 7.6.4 — fixed in 7.6.5
FortiOS 7.4: all versions 7.4
FortiOS 7.2: all versions 7.2
FortiProxy 7.6: from 7.6.0 to 7.6.4 — fixed in 7.6.5
FortiProxy 7.4: all versions 7.4
FortiProxy 7.2: all versions 7.2 (from the advisory and NVD; check the exact builds in the official advisory)

CVSS score

3.4

Actively exploited

Not known at this time

Source

Fortinet PSIRT – original advisory

Published

July 14, 2026

The description and the recommended action are quoted from the public advisory (the action is our generic advice); severity, exploitation status and affected versions are compiled automatically from public sources and may contain errors. The vendor's original advisory prevails: check it before taking action. This information is provided without warranty and does not replace a professional assessment.