Unsupported protocol during HTTPS access:...

FortiGate

FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.

Article Id 241702

Description

This article describes the unsupported protocol during HTTPS access: ERR_SSL_VERSION_OR_CIPHER_MISMATCH

Scope

FortiGate.

Solution

The issue appears when a user is trying to get HTTPS access to FortiGate even if HTTPS and SSH access is allowed on the port.

Error code: ERR_SSL_VERSION_OR_CIPHER_MISMATCH

This error occurs when the client and server do not support a common SSL protocol version or use an old TLS version.

Related document:

https://community.fortinet.com/t5/FortiCache/Technical-Tip-Low-Encryption-LENC-device-FAQ/ta-p/19032...

To check the TLS version configured in the FortiGate use the below command:

# sh full system global | grep tls

set admin-https-ssl-versions tlsv1-1

Config admin-https-ssl-versions to support more TLS protocols

# config system global

set admin-https-ssl-versions tlsv1-2

end

It is possible now, to try to access the GUI again:

9351

Contributors

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Technical Tip: Unsupported protocol during HTTPS access: ERR_SSL_VERSION_OR_CIPHER_MISMATCH

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