http Server Read Access
Impact
The web server allows remote users to read arbitrary
files on the system. If the password or shadow file
can be read, the attacker could crack account passwords
and gain access to the system.
Background
Web servers normally service requests for files under
their document root directory. For example, if server
has its root directory in /var/www/htdocs, and
it receives a request for http://server/page.html,
it sends the file /var/www/htdocs/page.html back
to the client.
The Problem
Operating systems allow path names to refer to a parent
directory using the "../" string. An attacker
could attempt to exploit this feature to retrieve files
from directories outside of the document root directory.
Web servers normally remove the "../" strings
from URLs. However an attacker can trick the web server
into accepting a "../" by encoding the dots into
their hexadecimal ASCII representation. Thus a pathname
including one or more instances of the string
"%2E%2E/" could be used to retrieve arbitrary
files from the server.
Resolutions
Contact the vendor of the web server for a fix. If
a fix is unavailable, it would be advisable to choose
a different web server.
Where can I read more about this?
For an example of this vulnerability, see
Bugtraq
and CORE-SDI.