Is CVE-2026-121528 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-121528 being exploited in the wild.

How severe is CVE-2026-121528?

High severity, with a CVSS score of 8.1, published 11 November 2026.

Which products and versions are affected?

Fortinet FortiOS 7.2.0 through 7.2.13, 7.4.0 through 7.4.9, 7.6.0 through 7.6.4.

How is CVE-2026-121528 attacked?

It is attacked over the network, in a network appliance.

Am I affected by CVE-2026-121528?

Check whether you run Fortinet FortiOS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-121528: Fortinet FortiOS improper certificate validation in SSLVPN

CVE-2026-121528 · Severity: high · CVSS 8.1 · Published 2026-11-11

FortiOS is a network operating system that powers firewalls and VPN appliances protecting corporate networks. An improper certificate validation flaw in the SSLVPN web portal allows unauthenticated attackers to intercept and modify encrypted traffic between VPN users and backend destinations, potentially exposing sensitive data or enabling credential theft.

Technologies: Fortinet FortiOS. Vendors: Fortinet.

Quick answers

Is CVE-2026-121528 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-121528 being exploited in the wild.
How severe is CVE-2026-121528?: High severity, with a CVSS score of 8.1, published 11 November 2026.
Which products and versions are affected?: Fortinet FortiOS 7.2.0 through 7.2.13, 7.4.0 through 7.4.9, 7.6.0 through 7.6.4.
Is there a fix for CVE-2026-121528?: Yes: fixed in FortiOS 7.2.14, 7.4.10, 7.6.5, or 8.0 and above. Until then: In fixed versions, configure "config vpn ssl setting set remote-https-cert-check reject-on-error" to reject connections with certificate validation errors instead of the default warn-on-error behavior. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-121528 attacked?: It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-121528?: Check whether you run Fortinet FortiOS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: FortiOS 7.2.14, 7.4.10, 7.6.5, or 8.0 and above

In fixed versions, configure "config vpn ssl setting set remote-https-cert-check reject-on-error" to reject connections with certificate validation errors instead of the default warn-on-error behavior.

Technical details

The vulnerability is an improper certificate validation (CWE-295) in the SSLVPN component that fails to properly validate HTTPS certificates on backend connections. An unauthenticated remote attacker can perform a man-in-the-middle attack by presenting a forged certificate, which the SSLVPN portal will accept. The vulnerability affects FortiOS versions 7.2.0–7.2.13, 7.4.0–7.4.9, and 7.6.0–7.6.4; versions 8.0 and later are unaffected.

Affected products

Fortinet FortiOS 7.2.0 through 7.2.13, 7.4.0 through 7.4.9, 7.6.0 through 7.6.4

Timeline

2026-11-10: disclosed
2026-11-11: advisory

References

https://fortiguard.fortinet.com/psirt/FG-IR-26-193

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.