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Google Gmail cross-site request forgery vulnerability

Google Gmail cross-site request forgery vulnerability

Overview

According to public reports, Google Gmail contained a cross-site request forgery (XSRF) vulnerability that allowed attackers to create email filters that could forward mail and attachments to arbitrary email addresses.

I. Description

Google Gmail is a web based mail service. Gmail provides support for email filters that allow users to sort and forward mail.

According to a report on the GNUCITIZEN site, Gmail contained a cross-site request forgery (XSRF) vulnerability that allowed attackers to create mail filters and forward mail to arbitrary email addresses. To exploit this vulnerability, an attacker would have had to convince a user to click or open a specially crafted hyperlink while the user was logged into their Gmail account. The hyperlink would have contained a http POST request that created the mail filter.

II. Impact

A remote attacker could have collected email addresses, emails, and attachments from a user's Gmail account.

III. Solution

According to publicly available reports, Google has addressed this vulnerability.

The following workarounds may partially mitigate future cross-site scripting (XSS) and XSRF vulnerabilities.

Workarounds for Users

• Using Gmail's SMTP and POP servers to send and receive mail will mitigate vulnerabilities in the Gmail web interface.
• The NoScript Firefox extension may mitigate XSRF and XSS vulnerabilities by restricting what sites can execute javascript and send cross-site POST requests.
• Encrypting sensitive emails and attachments will limit the impact of XSRF or other authentication bypass vulnerabilities.

Workarounds for Administrators

• Blacklisting known XSS or XSRF exploit URLs using proxy server or application firewall rules at the network permiter may prevent some vulnerabilities from being exploited. Note that this workaround will not stop all known XSS or XSRF attack vectors.

Systems Affected

Vendor	Status	Date Updated
Google	Vulnerable	1-Oct-2007

References

http://www.gnucitizen.org/blog/google-gmail-e-mail-hijack-technique/
http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html
http://mail.google.com/support/bin/answer.py?hl=en&answer=13273
http://noscript.net/
http://www.cert.org/homeusers/email_postcard.html

Credit

Information about this vulnerability was disclosed on the GNUCITIZEN website.

This document was written by Ryan Giobbi.

Other Information

Date Public	25.09.2007
Date First Published	01.10.2007 11:30:17
Date Last Updated	01.10.2007
CERT Advisory
CVE Name
Metric	0,79
Document Revision	15

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