FORTINET Security Advisory
Published Date: July 14, 2026
Advisory Summary
Fortinet has disclosed a security issue classified as Improper Neutralization of CRLF Sequences in HTTP Headers, also known as HTTP Response Splitting (CWE-113). This flaw affects FortiOS and FortiProxy products and could allow an attacker holding a valid web filter override token to inject arbitrary HTTP headers. The attack vector involves tricking a user into clicking a specially crafted link, which could enable various malicious activities such as web cache poisoning or cross-site scripting.
The vulnerability holds a CVSSv3 score of 3.4, indicating a moderate risk level but noteworthy due to its exploitation complexity involving social engineering. Fortinet has revised this security advisory on July 14, 2026, and it is critical for organizations using these products to verify their exposure and implement recommended patches or mitigations promptly.
- Assess FortiOS and FortiProxy instances to identify potential exposure.
- Review web filter override token management practices.
- Educate users to be cautious with unsolicited or suspicious links that may trigger malicious header injections.
- Apply security patches or updates as released by Fortinet to address this vulnerability.
Keeping infrastructure defenses updated continues to be essential in safeguarding the integrity of network communications and preventing exploitation of header injection attacks.
Reference: Vendor Advisory