Advisory Details

This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of WebGate WinRDS. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.

The specific flaw exists within the WESPPlayback.WESPPlaybackCtrl.1 control. The StopSiteAllChannel method copies arbitrary data to a fixed-size stack buffer. This would allow an attacker to execute arbitrary code in the context of the browser.

This vulnerability is being disclosed publicly without a patch in accordance with the ZDI 120 day deadline.

02/10/2014 - ZDI sent email to vendor requesting contact for disclosure
02/18/2014 - ZDI sent email to vendor requesting contact for disclosure
03/07/2014 - ZDI requested ICS-CERT assistance contacting the vendor
04/07/2014 - ZDI disclosed to ICS-CERT
ZDI has since sent multiple mails to ICS-CERT and kn-cert@ncsc.go.kr regarding Webgate cases in general. However, to ZDI's knowledge, this has not resulted in any vendor response.

-- Mitigation:
The killbit can be set on this control to disable scripting within Internet Explorer by modifying the data value of the Compatibility Flags DWORD within the following location in the registry:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\4E14C449-A61A-4BF7-8082-65A91298A6D8
If the Compatibility Flags value is set to 0x00000400, the control can no longer be instantiated inside the browser.
For more information, please see: http://support.microsoft.com/kb/240797

• 2014-02-10 - Vulnerability reported to vendor
• 2015-02-27 - Coordinated public release of advisory