IR Number FG-IR-17-168
Date Nov 3, 2017
Severity light-circle-logo light-circle-logo light-circle-logo light-circle-logo light-circle-logo Medium
Impact Cross-site Scripting (XSS)
CVE ID CVE-2017-7739
Affected Products
FortiOS : 5.6.0, 5.4.5, 5.4.4, 5.4.3, 5.4.2, 5.4.1, 5.4.0, 5.2.9, 5.2.8, 5.2.7, 5.2.6, 5.2.5, 5.2.4, 5.2.3, 5.2.2, 5.2.11, 5.2.10, 5.2.1, 5.2.0
CVRF Download

PSIRT Advisories

FortiOS Reflected XSS in Web Proxy Disclaimer Response web page

Summary

A reflected XSS vulnerability exists in FortiOS web proxy disclaimer response web pages, potentially  exploitable by an unauthenticated attacker, via sending a maliciously crafted URL to the victim. The victim visiting the malicious URL would then have arbitrary javascript code executed in the security context of her/his browser.

Affected Products

FortiOS 5.6.0
FortiOS 5.4.0 to 5.4.5
FortiOS 5.2.0 to 5.2.11

Solutions

Upgrade to FortiOS 5.2.12, 5.4.6 or 5.6.1

Workaround

In System->Replacement Messages->Web-proxy->"Web-proxy HTTP Error Page", remove the following default message content: 
              URL: %%PROTOCOL%%://%%URL%%

Update Revisions

2018-05-14 Add workaround for old FortiOS versions.
2017-11-03 Initial version.

Acknowledgement

Fortinet is pleased to thank "usd AG" and "Serge Ivanov of Payvision BV" for reporting this vulnerability under responsible disclosure.