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Vulnerability Note VU#713779Microsoft MSN Messenger Chat Control contains a buffer overflow in "ResDLL" parameterOverviewMicrosoft's MSN Chat is an ActiveX control for Microsoft Messenger, an instant messaging client. A buffer overflow exists in the ActiveX control that may permit a remote attacker to execute arbitrary code on the system with the privileges of the current user.I. DescriptionA buffer overflow exists in the "ResDLL" parameter of the MSN Chat ActiveX control that may permit a remote attacker to execute arbitrary code on the system with the privileges of the current user. This vulnerability affects MSN Messenger and Exchange Instant Messenger users. Since the control is signed by Microsoft, users of Microsoft's Internet Explorer (IE) who accept and install Microsoft-signed ActiveX controls are also affected. The Microsoft MSN Chat control is also available for direct download from the web.The <object> tag could be used to embed the ActiveX control in a web page. This vulnerability could be exploited if an attacker can trick the user into visiting a malicious site or the attacker sends the victim a web page as an HTML-formatted email message or newsgroup posting. This acceptance and installation of the control can occur automatically within IE for users who trust Microsoft-signed ActiveX controls. When the web page is rendered, either by opening the page or viewing the page through a preview pane, the ActiveX control could be invoked. Likewise, if the ActiveX control is embedded in a Microsoft Office (Word, Excel, etc.) document, it may be executed when the document is opened.
II. ImpactA remote attacker can execute arbitrary code on the target machine with the privileges of the current user.III. SolutionOn June 11, 2002, Microsoft updated Microsoft Advisory (MS02-022) and released a new patch that remedies the vulnerability for users that downloaded and accepted the control. The previous solution did not fully protect against this action and it was possible for an attacker to load the vulnerable control, even though the previous patch and updated versions had been installed.
Updated version of MSN Chat control Updated version of MSN Messenger with the corrected control Updated version of Exchange Instant Messenger with the corrected control Microsoft also suggests that the email attack vector is blocked by the following Microsoft mail products: Outlook 98 and Outlook 2000 with the Outlook Email Security Update, Outlook 2002, and Outlook Express. All of these products will open HTML email in the Restricted Sites zone. Other mitigation strategies include opening web pages and email messages in the Restricted Sites zone and using email clients that permit users to view messages in plain-text. Likewise, it is important for users to realize that a signed control only authenticates the origin of the control and does not imply any information with regard to the security of the control. Therefore, downloading and installing signed controls through an automated process is not a secure choice. Systems Affected
Referenceshttp://www.cert.org/reports/activeX_report.pdf Our thanks to eEye for their analysis and report on this vulnerability. This document was written by Jason Rafail.
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