From: Secunia Security Advisories (sec-advsecunia.com)
Date: Mon Oct 03 2005 - 10:09:57 CDT

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TITLE:
Citrix Metaframe Presentation Server Policy Filtering Bypass

SECUNIA ADVISORY ID:
SA17032

VERIFY ADVISORY:
http://secunia.com/advisories/17032/

CRITICAL:
Moderately critical

IMPACT:
Security Bypass

WHERE:
From remote

SOFTWARE:
Citrix Presentation Server 4.x
http://secunia.com/product/5270/
Citrix MetaFrame Presentation Server 3.x
http://secunia.com/product/3805/

DESCRIPTION:
Gustavo Gurmandi has reported a vulnerability in Citrix MetaFrame
Presentation Server, which can be exploited by malicious users to
bypass certain security restrictions.

The vulnerability is caused due to a validation error when policy
filtering decisions are made based on the user's client name. This
can be exploited by malicious users to bypass certain policy
restrictions by modifying the client name in the "launch.ica" file

The vulnerability has been reported in the following versions:
* Citrix MetaFrame Presentation Server 3.0 for Microsoft Windows
2000
* Citrix MetaFrame Presentation Server 3.0 for Microsoft Windows
2003
* Citrix Presentation Server 4.0 for Microsoft Windows 2000
* Citrix Presentation Server 4.0 for Microsoft Windows 2003

SOLUTION:
Do not use client names for policy filtering decision.

PROVIDED AND/OR DISCOVERED BY:
Gustavo Gurmandi, GrupoITPro Security Research Community.

ORIGINAL ADVISORY:
Citrix:
http://support.citrix.com/kb/entry!default.jspa?categoryID=275&externalID=CTX107705

GrupoITPro Security Research Community:
http://www.grupoitpro.com.ar/ctxpoliciesbypass.txt

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