CVE-2025-62826 Fortinet CVE debrief

Who should care

Organizations using Fortinet FortiOS and FortiProxy, especially those with exposed instances or sensitive data, should be aware of this vulnerability and take steps to mitigate it. This includes reviewing their deployments, applying patches or mitigations, and monitoring for suspicious activity. Security teams and vulnerability management teams should prioritize patching vulnerable versions to prevent potential HTTP response splitting attacks.

Technical summary

CVE-2025-62826 is an Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability in Fortinet FortiOS 7.6.0 through 7.6.4, FortiOS 7.4 all versions, FortiOS 7.2 all versions, FortiProxy 7.6.0 through 7.6.4, FortiProxy 7.4 all versions, FortiProxy 7.2 all versions. The vulnerability may allow an attacker able to intercept and modify a user's captive portal authentication request to inject arbitrary headers via crafted HTTP requests. This could lead to potential HTTP response splitting attacks, allowing attackers to manipulate HTTP responses.

Defensive priority

Organizations using Fortinet FortiOS and FortiProxy should prioritize patching vulnerable versions to prevent potential HTTP response splitting attacks.

Recommended defensive actions

• Apply patches for Fortinet FortiOS 7.6.0 through 7.6.4, FortiOS 7.4 all versions, FortiOS 7.2 all versions, FortiProxy 7.6.0 through 7.6.4, FortiProxy 7.4 all versions, FortiProxy 7.2 all versions
• Monitor for suspicious HTTP requests
• Verify captive portal authentication requests for potential tampering
• Implement additional security measures to detect and prevent HTTP response splitting attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE-2025-62826 record indicates an Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') vulnerability in Fortinet FortiOS and FortiProxy. The vulnerability, with a CVSS score of 3.1, may allow an attacker to inject arbitrary headers via crafted HTTP requests if they can intercept and modify a user's captive portal authentication request.

Official resources