[CVE-2021-22885] Possible Information Disclosure / Unintended Method Execution in Action Pack

[Aaron Patterson]

There is a possible information disclosure / unintended method execution

vulnerability in Action Pack which has been assigned the CVE identifier

CVE-2021-22885.

Versions Affected:  >= 2.0.0.

Not affected:       < 2.0.0.

Fixed Versions:     6.1.3.2, 6.0.3.7, 5.2.4.6, 5.2.6

Impact

------

There is a possible information disclosure / unintended method execution

vulnerability in Action Pack when using the `redirect_to` or `polymorphic_url`

helper with untrusted user input.

Vulnerable code will look like this:

```

redirect_to(params[:some_param])

```

All users running an affected release should either upgrade or use one of the

workarounds immediately.

Releases

--------

The FIXED releases are available at the normal locations.

Workarounds

-----------

To work around this problem, it is recommended to use an allow list for valid

parameters passed from the user.  For example:

```

private def check(param)

  case param

  when "valid"

    param

  else

    "/"

  end

end

def index

  redirect_to(check(params[:some_param]))

end

```

Or force the user input to be cast to a string like this:

```

def index

  redirect_to(params[:some_param].to_s)

end

```

Patches

-------

To aid users who aren't able to upgrade immediately we have provided patches for

the two supported release series. They are in git-am format and consist of a

single changeset.

* 5-2-information-disclosure.patch - Patch for 5.2 series

* 6-0-information-disclosure.patch - Patch for 6.0 series

* 6-1-information-disclosure.patch - Patch for 6.1 series

Please note that only the 5.2, 6.0, and 6.1 series are supported at present. Users

of earlier unsupported releases are advised to upgrade as soon as possible as we

cannot guarantee the continued availability of security fixes for unsupported

releases.

Credits

-------

Thanks to Benoit Côté-Jodoin from Shopify for reporting this.

--

Aaron Patterson
http://tenderlovemaking.com/