Advisory: Arbitrary Redirect in Tuleap

RedTeam Pentesting discovered an arbitrary redirect vulnerability in the
redirect mechanism of the application lifecycle management platform
Tuleap.


Details
=======

Product: Tuleap
Affected Versions: > 9.17.99.93
Fixed Versions: >= 9.17.99.93
Vulnerability Type: Arbitrary Redirect
Security Risk: low
Vendor URL: https://www.tuleap.org/
Vendor Status: fixed version released
Vendor Issue URL: https://tuleap.net/plugins/tracker/?aid=11136
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2018-001
Advisory Status: published
CVE: GENERIC-MAP-NOMATCH
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=GENERIC-MAP-NOMATCH


Introduction
============

"Tuleap is an open source tool for Scrum, Kanban, waterfall,
requirement management. Plan, track, code and collaborate on software
projects, you get everything at hand."
(from the Tuleap website [1])


More Details
============

RedTeam Pentesting discovered an arbitrary redirect vulnerability in the
way Tuleap handles redirects. Usually this function is only used in
Tuleap after an successful login to assigned trackers, however the
redirect can be used indepented of whether a user is authenticated to
the application. While the application employs a URL filter to prevent
arbitrary redirects, the URL filter can be bypassed. This allows
attackers to redirect users to a different website, if a user opens an
attacker prepared URL. 

The filter can be bypassed by using protocol relative URLs, which omit
the leading protocol identifier. These arbitrary URLs are prefixed with
two slashes, which instructs the browser to use the same protocol as the
current page. This behaviour is specified in RFC 3986 [2] in section
5.4.


Proof of Concept
================

The following URL to an example installation of Tuleap will redirect
users to an attacker controlled website:

https://example.net/my/redirect.php?return_to=//attacker.com


Workaround
==========

Currently no workaround is known.


Fix
===

Upgrade to at least tuleap version 9.17.99.93. 


Security Risk
=============

Attackers may convice users to use a prepared link to access a valid
Tuleap instance, which then redirects users to a fake login page. This
can greatly increase the effectiveness of phishing attacks and may allow
attackers to steal user credentials more effectively.  However, no
credentials or sensitive information can be extracted directly.
Furthermore, the website to which users are going to be redirected will
be displayed in the browser location bar so that users may identify the
attack. Therefore, we rate this vulnerability with a low risk.

Nevertheless, it is very easy for attackers to identify this
vulnerability and create malicious URLs, which makes it very likely that
attackers might abuse this. 


Timeline
========

2018-01-02 Vulnerability identified
2018-01-11 Customer approved disclosure to vendor
2018-02-13 Vendor notified
2018-02-14 Vendor released fixed version
2018-03-05 Vendor made issue public 
2018-03-08 Advisory released 


References
==========

[1] https://www.tuleap.org/what-is-tuleap
[2] https://tools.ietf.org/html/rfc3986


RedTeam Pentesting GmbH
=======================

RedTeam Pentesting offers individual penetration tests performed by a
team of specialised IT-security experts. Hereby, security weaknesses in
company networks or products are uncovered and can be fixed immediately.

As there are only few experts in this field, RedTeam Pentesting wants to
share its knowledge and enhance the public knowledge with research in
security-related areas. The results are made available as public
security advisories.

More information about RedTeam Pentesting can be found at:
https://www.redteam-pentesting.de/


Working at RedTeam Pentesting
=============================

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in Aachen, Germany. If you are interested please visit:
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