Real reported this flaw on 20050916:

Remote exploitation of a heap-based buffer overflow could allow the execution of
arbitrary code in the context of the currently logged in user.

The vulnerability specifically exists in the handling of the 'chunked'
Transfer-Encoding method.

Successful exploitation allows a remote attacker to execute arbitrary code with
the privileges of the currently logged in user. In order to exploit this
vulnerability, an attacker would need to entice a user to follow a link to a
malicious server. Once the user visits a website under the control of an
attacker, it is possible in a default install of RealPlayer to force a
web-browser to use RealPlayer to connect to an arbitrary server, even when it is
not the default application for handling those types, by the use of embeded
object tags in a webpage. This may allow automated exploitation when the page is
viewed.

As the client sends its version information as part of the request, it would be
possible for an attacker to create a malicious server which uses the appropriate
offsets and shellcode for each version and platform of the client.

Possible embargo is 20051018