SEC Consult Vulnerability Lab Security Advisory < 20111012-0 >
title: Client-side remote file upload & command execution
product: Microsoft Forefront Unified Access Gateway Remote
Access Agent (signed Java applet)
vulnerable version: 22.214.171.124
CVE number: CVE-2011-1969
by: Elisabeth Demeter / SEC Consult Vulnerability Lab
"Forefront Unified Access Gateway 2010 (UAG) delivers comprehensive, secure
remote access to corporate resources for employees, partners, and vendors on
both managed and unmanaged PCs and mobile devices. Utilizing a combination of
connectivity options, ranging from SSL VPN to Direct Access, as well as built
in configurations and policies, Forefront UAG provides centralized and easy
management of your organization's complete anywhere access offering.
Integrating a deep understanding of the applications published, the state of
health of the devices being used to gain access, and the user's identity –
Forefront UAG enforces granular access controls and policies to deliver
comprehensive remote access, ensure security, and reduce management costs
The client-side endpoint security solution (Microsoft Forefront UAG), e.g.
supplied by Microsoft Outlook Web App, uses either a signed Java applet
(Remote Access Agent) or an ActiveX Control (Endpoint Components) to connect
to a VPN and perform local compliance scans on the client.
Due to quality issues within the software, an attacker is able to access
insecure methods from the "trustworthy" Java applet and exploit those features
to compromise all client systems that trust the correctly signed Java applet
(e.g. all users that need to use this software for accessing internal systems
over company VPN).
The ActiveX control has the same functionality, which is why it is strongly
presumed that a similar attack is possible.
Microsoft UAG Remote Access Agent contains the MicrosoftClient.jar which in
turn contains AgentAppletDriver.java. This class creates an "Agent" object
that writes one of the following three files to the client system (depending
on the operating system):
It is only checked if the jar is signed, but not who signed it, so any created
self-signed jar that is named like one of these files can be used. The
manipulated jar files can only be loaded if the codebase is completely on the
attacker system (the MicrosoftClient.jar and all the other needed files need
to be on the attacker system).
The agent_xxx_helper.jar needs to include any executable with the name
"ProxyProcess_Win.exe" and/or "AttachmentWiper.exe" which is executed during
the doInit() function which in turn is called during the init() function of
Summing up, an attacker is able to upload arbitrary executable files to remote
clients and then immediately execute them without notice as a signed Java
applet is being used (if "Always trust content from this publisher" has been
checked - otherwise an unsuspicious Java digital signature verification popup
Possible attack vectors are drive-by downloads just by visiting malicious
websites but also through emails, any XSS on unsuspicous websites, etc.
Proof of concept:
The exploit will not be published, but a video demonstrating this issue has
been created. It can be found at the following URL:
Vulnerable / tested versions:
The Forefront UAG Remote Access Agent 126.96.36.199 has been tested and successfully
Vulnerable signed Java applet certificate SHA1 fingerprint:
According to Microsoft, the following systems are vulnerable:
- Microsoft Forefront Unified Access Gateway 2010
- Microsoft Forefront Unified Access Gateway 2010 Update 1
- Microsoft Forefront Unified Access Gateway 2010 Update 2
- Microsoft Forefront Unified Access Gateway 2010 Service Pack 1
Vendor contact timeline:
2011-04-22: Contacted vendor through firstname.lastname@example.org
2011-04-22: Vendor: Very fast response, issue is being investigated:
MSRC case 11257
2011-04-28: Contacted vendor asking for updates
2011-05-17: Contacted vendor again asking for updates
2011-05-19: Contacted personal contact at MSRC asking for updates
2011-05-19: Answer from personal contact and from case manager: they could reproduce
the issue and are currently working on a fix timeline, fix expected in
the next few months
2011-05-30: Contacted vendor informing about our publishing schedule: minimal
information will be published on June 13th, mutual customers will be
informed in more detail, advisory and video will be published when issue
2011-05-31: Answer from vendor to postpone the publishing date
2011-06-06: Proposal to the vendor to postpone the publishing date to July 12th
2011-06-06: Answer from vendor ok-ing it
2011-06-22: Update from vendor to postpone the publishing date again
2011-06-23: Update from vendor with more information about the fixing schedule
2011-06-28: Contacted vendor accepting a possible postponing of the July 12th
publishing date, also offering dates for a phone-conference call
2011-06-28: Answer from vendor about dates for phone-conference call
2011-06-29: New offering of dates for phone-conference call
2011-07-13: Conference call
2011-08-21: Contacted vendor about updates
2011-08-22: Update from third party will be in october, so patch from vendor will also be in october
2011-09-26: Contacted vendor about specific publishing dates
2011-09-26: Publishing dates confirmed by vendor for October 11th
We thank the people from Microsoft for their cooperation!
Update your Microsoft Forefront UAG.
Deactivate Java in your browser. Login to Microsoft Outlook Web App should
still be possible.
Add the entry for the following file:
# UAG Client MicrosoftClient.jar
Remove the affected trusted certificate (see fingerprint above) of Microsoft
Corporation from the Java control panel (jcontrol) from all clients.
Don't fully trust signed Java applets (in general).
This workaround can be applied to MAC, Linux, and Windows systems by
modifying the appropriate blacklist file on each system.
If the VPN functionality (or any other) is absolutely needed, only "trust"
it on the company site (don't store the certificate forever and verify each
connect) and don't click on it when the Java certificate popup occurs on other
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Mail: research at sec-consult dot com
EOF E. Demeter / 2011