Some Fortinet products used hardcoded keys and weak encryption for communications

Researchers at SEC Consult Vulnerability Lab discovered multiple issues in several security products from Fortinet, including hardcoded key and encryption for communications.

Security researchers from SEC Consult Vulnerability Lab discovered that multiple Fortinet products use a weak encryption cipher (“XOR” with a static key) and cryptographic keys to communicate with the FortiGuard Web Filter, AntiSpam and AntiVirus cloud services.

An attacker could exploit the issues to eavesdrop on user traffic and manipulate it.

The flaw discovered by SEC Consult Vulnerability Lab researchers has been tracked as CVE-2018-9195, the experts also published a proof-of-concept (PoC) code to trigger it.

The PoC code is a Python 3 script that decrypts a FortiGuard message.

“Fortinet products, including FortiGate and Forticlient regularly send information to Fortinet servers (DNS: guard.fortinet.com) on

• UDP ports 53, 8888 and
• TCP port 80 (HTTP POST /fgdsvc)

This cloud communication is used for the FortiGuard Web Filter feature, FortiGuard AntiSpam feature and FortiGuard AntiVirus feature.” reads the analysis published by the experts.

“The messages are encrypted using XOR “encryption” with a static key.”

The vulnerability affects versions of FortiOS (before 6.0.7 or 6.2.0), FortiClient for Windows before 6.2.0, and FortiClient for Mac before 6.2.2.

Fortinet also published a security advisory on the vulnerability.

“Use of a hardcoded cryptographic key in the FortiGuard services communication protocol may allow a Man in the middle with knowledge of the key to eavesdrop on and modify information (URL/SPAM services in FortiOS 5.6, and URL/SPAM/AV services in FortiOS 6.0.; URL rating in FortiClient) sent and received from Fortiguard severs by decrypting these messages.” reads the advisory published by FortiGuards Labs.

Fortinet credited Stefan Viehböck for the flaw, the researcher and responsibly reported it to Fortinet on May 16, 2018.

Experts at SEC Consult pointed out that by intercepting and manipulating internet traffic an attacker can alter the responses for FortiGuard Web Filter, AntiSpam and AntiVirus features.

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Pierluigi Paganini

(SecurityAffairs – Fortinet, hacking)

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