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From "Carl K." <c...@etrak-plus.com>
Subject Re: Vulnerability from PCI scan
Date Tue, 01 Nov 2016 22:05:22 GMT


On 11/1/2016 5:25 PM, Christopher Schultz wrote:
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> Carl,
>
> On 11/1/16 5:11 PM, Carl K. wrote:
>> Control Scan has returned this as a vulnerability in Tomcat
>> 8.0.38:
>>
>> Vulnerable version of Apache Tomcat: 8.0.38
>>
>> Risk: High (3) Port: 443/tcp Protocol: tcp Threat ID:
>> web_dev_tomcatver
>>
>> Details: 404 Error Page Cross Site Scripting Vulnerability
>> 12/21/09 Apache Tomcat is prone to a cross-site scripting
>> vulnerability because it fails to properly sanitize user-supplied
>> input. An attacker may leverage this issue to execute arbitrary
>> script code in the browser of an unsuspecting user in the context
>> of the affected site. Apache Tomcat mitigates HTTP_PROXY
>> environment variable "httpoxy" issue
>>
>> I have read everything I can find and it still doesn't make
>> sense... can someone help to point me in the correct direction?
>>
>> I am further puzzled because this is the first time this has come
>> up and we run Tomcat for years... note that the date is listed as
>> 12-21-2009.
> Technically, this is not a vulnerability in Tomcat (or any
> reverse-proxy, such as httpd) but it does represent a failure to
> protect stupid command-line utilities from making bad decisions about
> trusting environment variables.
>
> Long story short, if using the CGI Servlet, any headers coming from
> the request are set as HTTP_* environment variables on a script that
> is executed as a CGI script. Notably, python, Perl, and PHP (and
> others) use an environment variable called HTTP_PROXY to indicate the
> presence of a forward-proxy to be used for outgoing HTTP connections.
> Thus, setting a "Proxy" header in an HTTP request to Tomcat will
> result in a CGI script seeing that value in the HTTP_PROXY environment
> variable. This could present a problem in your environment, but is
> possible to mitigate in a number of different ways.
>
> https://www.apache.org/security/asf-httpoxy-response.txt
>
> I have no idea where your scanner got the date 2009-12-21. Perhaps
> they took the recently-disclosed CVE (CVE-2016-5388 -- note the year
> on that CVE identifier) and made a best-guess of when the product was
> first vulnerable. The first beta version of Tomcat 7 wasn't available
> until 2010, so perhaps they were considering Tomcat 6 as well. But
> Tomcat 6's history goes back well before that. Honestly, I think they
> may have picked that date out of the air.
>
> At any rate, you are safe if any of the following are true:
>
> 1. You don't use the CGI servlet
> 2. You don't use any scripts that use HTTP_PROXY in this manner
>     (this is a weak criteria, since you may not KNOW if you are using
>      such scripts)
> 3. You don't allow outgoing HTTP requests from your application servers,
>     and no error messages produces by those scripts would leak any
>     information like URLs, etc.
> 4. If you have a reverse-proxy (e.g. httpd) and explicitly remove any
>     "proxy" headers from incoming HTTP requests
>
> Mitigation is possible through a variety of means. If you aren't
> vulnerable, this scan is likely to complain merely because of the
> version number of Tomcat and the fact that this CVE hasn't officially
> been closed, yet.
That is about where I had gotten to.

I really appreciate your quick and thorough response.

Carl



>
> - -chris
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