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Re: [ANN] Struts 2 up to 2.3.16.1: Zero-Day Exploit Mitigation (security | critical)
From: Rene Gielen <rgielen () apache org>
Date: Fri, 25 Apr 2014 20:08:49 +0200

Hi,

Am 25.04.14 18:52, schrieb Tim:


So I have to say, I feel like the Struts team is kind of... failing.
Here are my gripes:

A) I questioned the last bug fix in the thread here [1], where we
   were all reassured that it was just "ClassLoader manipulation", not 
   RCE.  Clearly that's not true.


At this point in time, it was true. The RCE is not exactly a Struts
issue alone, the Struts issue just opens the door to an unprotected
field in a certain servlet container environment.

B) The fix for the last CVE was that crappy "^class\." filter, which
   I pointed out was insufficient.  The Struts team quickly fixed
   that, but never bothered to update the "workaround" section in the 
   last advisory to the less-terrible ".*\.class\..*" regex (or whatever
   it was).  So if developers just implemented the work around from
   the advisory, they were obviously not protected.  (In hindsight,
   they never were protected even with the better regex, but was just
   irresponsible not to make the second regex more public.)


Better suggestions are always welcome. We have a mail address to reach
us for any concerns regarding security: security () struts apache org

C) The Struts team is playing whack-a-mole.  Instead of fixing the
   root issue, they are just adding one blacklist regex after another,
   hoping no one figures out yet another way around it.


We try to protect users who are not using a properly configured security
manager, as it is always recommended when working with application
servers. Sometimes we seem to fail, indeed. As others, we don't seem to
be perfect. BTW, we are not only blacklisting - the blacklist is applied
for special cases that make it through the whitelist.


I urge you to take OGNL and *throw it out*.  Replace it with something
that allows only a white list of properties to be set, based on what
the application defines as relevant.  Until then, I'm recommending to
my clients that they avoid Struts like the plague.


To what alternative? UEL? The attack vector is just using a simple
getter semantic which basically works with any EL. Throwing out EL
capabilities is no option for most users. Anyway, if somebody likes to
help with more than just fingerpointing, he/she is heartly welcome!

Regards
René

tim

1. http://seclists.org/fulldisclosure/2014/Mar/53



On Thu, Apr 24, 2014 at 05:37:13PM +0200, Rene Gielen wrote:
In Struts 2.3.16.1, an issue with ClassLoader manipulation via request
parameters was supposed to be resolved. Unfortunately, the correction
wasn't sufficient.

A security fix release fully addressing this issue is in preparation and
will be released as soon as possible.

Once the release is available, all Struts 2 users are strongly
recommended to update their installations.

* Until the release is available, all Struts 2 users are strongly
recommended to apply the mitigation described in [1] *

Please follow the Apache Struts announcement channels [2][3][4][5] to
stay updated regarding the upcoming security release. Most likely the
release will be available within the next 72 hours. Please prepare for
upgrading all Struts 2 based production systems to the new release
version once available.

- The Apache Struts Team.

[1] http://struts.apache.org/announce.html#a20140424
[2] http://struts.apache.org/mail.html
[3] http://struts.apache.org/announce.html
[4] https://plus.google.com/+ApacheStruts/posts
[5] https://twitter.com/TheApacheStruts

-- 
René Gielen
http://twitter.com/rgielen

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-- 
René Gielen
http://twitter.com/rgielen

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