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Category:   Application (Generic)  >   Blackboard Vendors:   Blackboard
Blackboard Learn Open Redirect Flaw in Shibboleth Authentication Provider Lets Remote Users Redirect the Target User's Browser to an Arbitrary Site
SecurityTracker Alert ID:  1040767
SecurityTracker URL:  http://securitytracker.com/id/1040767
CVE Reference:   CVE-2017-18262   (Links to External Site)
Date:  Apr 27 2018
Impact:   Modification of system information
Exploit Included:  Yes  

Description:   A vulnerability was reported in Blackboard. A remote user can redirect the target user's browser to an arbitrary site.

A remote user can create a URL that, when loaded by the target authenticated user, will redirect the target user's browser to an arbitrary site.

Sites using the Shibboleth authentication provider are affected.

The vendor was notified on October 17, 2017.

A demonstration exploit URL is provided:

https://[target]/webapps/bb-auth-provider-shibboleth-BBLEARN/execute/shibbolethLogin?returnUrl=[myEvilUrl]&authProviderId=realAuthProvider

Ethan Sweet reported this vulnerability.

Impact:   A remote user can cause the target authenticated user's browser to be redirected to an arbitrary web site.
Solution:   No solution was available at the time of this entry.
Vendor URL:  www.blackboard.com/ (Links to External Site)
Cause:   Input validation error

Message History:   None.


 Source Message Contents

Subject:  [FD] Unvalidated Redirect in Shibboleth component of Blackboard Learn

CVE-2017-18262



[Description]

Since at least the 17th of October 2017 (Initial report date) Blackboard Learn has allowed Unvalidated Redirects on any signed in user through its endpoints for handling Shibboleth logins.



The vulnerable endpoint is: 



BLACKBOARD/webapps/bb-auth-provider-shibboleth-BBLEARN/execute/shibbolethLogin?returnUrl=myEvilUrl&authProviderId=realAuthProvider



Where:

BLACKBOARD is the Blackboard Learn web server endpoint.

myEvilUrl is any URL you want, URL encoded of course.

realAuthProvider is the auth provider, normally you can just gather this by attempting a real shibboleth login and looking at what authProviderId is set to.



This attack only works against Blackboard Learn web servers with Shibboleth set up.



[Reproduction steps]



Set up a blackboard learn web server, make sure shibboleth is set up.

Copy the shibboleth login URL from the sign in page (should look like the endpoint above)

Replace the returnUrl with another URL (myEvilUrl).

Open the URL and log in as normal (if not already signed in properly to complete shibboleth login).

You will be redirected to the returnUrl you gave, regardless of what that url is.





[Type]

Unvalidated Redirect



[Vendor]

Blackboard Inc


[Discoverer]
Ethan Sweet



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