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From Tomas Hoger <>
Subject Re: [RFC] further proxy/rewrite URL validation security issue (CVE-2011-4317)
Date Thu, 12 Jan 2012 09:54:37 GMT
Jeff Trawick <trawick <at>> writes:

> >> Tomas Hoger tracked this down to a change to apr_uri_parse(), see here:
> >>
> >>
> >>
> >> The referenced change is in APR-util version 1.2.13, so httpd is not
> >> vulnerable if using APR-util 1.2.12 or older versions.
> >
> > Can we determine this to be errant behavior in apr_uri_parse?
> I think we can for at least a couple of these.  In fact I assumed
> based on the httpd 2.0 assessment pointed to earlier that the two URIs
> already were rejected, and so I expected these two URIs to fail to
> parse with apr-util 0.9.

These URIs do not fail to parse in older apr-util, but they are parsed in
a different way.  In recent versions, you get:

scheme: @localhost, path: :8880
scheme: qualys, path:

This does have path not starting with / (required for the attack) and
also non-NULL scheme (required to bypass "does uri start with /?" check
added in r1179239).

In older versions, you get:

scheme: (null), path: @localhost::8880
scheme: (null), path:

With NULL scheme, there's no bypass of r1179239.  AFAICS, when older
apr_uri_parse() returns non-NULL scheme, path is either NULL or it
starts with a /.


Tomas Hoger

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