K2 smartforms runtime application - 4.6.11 SSRF

From: fuming22@gmail.com
To: bugtraq@securityfocus.com
Subject: K2 smartforms runtime application - 4.6.11 SSRF

# Vulnerability type: Server Side Request Forgery
# Vendor: https://www.k2.com/
# Product: K2 Smartforms
# Affected version: 4.6.11
# Credit: Foo Jong Meng
# CVE ID: CVE-2018-9920


Server side request forgery exists in the runtime application in K2 smartforms 4.6.11 via a modified hostname in an https://*/Identity/STS/Forms/Scripts URL.

By replacing the "GET" parameter to any external domain (i.e. https://www.external-domain.com) while accessing the affected application (e.g.

The resulting page shows URL with https://url/Identity/STS/Forms/Scripts but rendering https://www.external-domain.com in the body (aka local web defacement). 

A port scan on the internal servers can be performed by changing the "GET" parameter URL and analysing the results of the return page.

1. Use a web proxy (i.e zapproxy, burp) to intercept "GET" request for:

2. Replace the "GET" parameter to any external domain (i.e. https://www.external-domain.com/)

3. The resulting page is one with https://url/Identity/STS/Forms/Scripts but showing https://www.external-domain.com/ in the body.

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