Vulnerability Note VU#612636

Google SAML Single Sign on vulnerability

Original Release date: 02 Sep 2008 | Last revised: 25 Sep 2008


The SAML Single Sign-On (SSO) Service for Google Apps contained a vulnerability that could have allowed an attacker to gain access to a user's Google account.


The Security Assertion Markup Language (SAML) is a standard for transmitting authentication data between two or more security domains. In SAML language, XML security packets are called assertions. Identity providers pass assertions to service providers who allow the requests. In the Google Single Sign on (SSO) implementation, the authentication response did not include the identifier of the authentication request or the identity of the recipient. This may allow a malicious service provider to impersonate a user at other service providers.

More technical information about this issue is available in the Formal Analysis of SAML 2.0 Web Browser Single Sign-On: Breaking the SAML-based Single Sign-On for Google Apps whitepaper which is available here:

Note that to exploit this vulnerability, the attacker would have to convince the user to login to their site.


A malicious service provider might have been able to access a user's Google Account or other services offered by different identity providers.


Google has addressed this issue by changing the behavior of their SSO implemenation. Administrators and developers were required to update their identity provider to provide a valid recipient field in their assertions.

Do not log into untrusted sites

To mitigate future vulnerabilities, users should use caution when providing their credentials to log into Google services via third party service providers.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
GoogleAffected18 Jun 200802 Sep 2008
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



Thanks to Alessandro Armando and the AVANTSSAR Project for reporting this issue and to Google for providing technical information and feedback

This document was written by Ryan Giobbi.

Other Information

  • CVE IDs: Unknown
  • Date Public: 13 Jun 2008
  • Date First Published: 02 Sep 2008
  • Date Last Updated: 25 Sep 2008
  • Severity Metric: 2.10
  • Document Revision: 21


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