EMBARGOED
CRD 2015-06-16

CSRF Vulnerability in jquery-ujs and jquery-rails

There is an vulnerability in jquery-ujs and jquery-rails that can be used to
bypass CSP protections and allows attackers to send CSRF tokens to attacker domains.

This vulnerability has been assigned the CVE identifier CVE-2015-1840.

Versions Affected:  All.
Not affected:       Applications which don't use jquery-ujs or jquery-rails.
Fixed Versions:     jquery-rails versions 4.0.4 and 3.1.3 and jquery-ujs 1.0.4.

Impact
------
In the scenario where an attacker might be able to control the href attribute of an anchor tag or
the action attribute of a form tag that will trigger a POST action, the attacker can set the
href or action to " https://attacker.com" (note the leading space) that will be passed to JQuery,
who will see this as a same origin request, and send the user's CSRF token to the attacker domain.

Releases
--------
The FIXED releases are available at the normal locations.

Workarounds
-----------
To work around this problem, change code that allows users to control the href attribute of an anchor
tag or the action attribute of a form tag to filter the user parameters.

For example, code like this:

    link_to params

to code like this:

    link_to filtered_params

    def filtered_params
      # Filter just the parameters that you trust
    end

Patches
-------
To aid users who aren't able to upgrade immediately we have provided patches for the
supported release series. They are in git-am format and consist of a single changeset.

* 1-0-3-jquery_ujs_csrf.patch - Patch for jquery-ujs 1.0.3.

* 3-1-2-jquery-rails-csrf.patch - Patch for jquery-rails 3.1.2.
* 4-0-3-jquery-rails-csrf.patch - Patch for jquery-rails 4.0.3.

Credits
-------

Thanks to Ben Toews of GitHub for reporting the vulnerability to us, and working with us on a fix.