The Ruby SAML library is for implementing the client side of a SAML authorization. Ruby-SAML in <= 12.2 and 1.13.0 <= 1.16.0 does not properly verify the signature of the SAML Response. An unauthenticated attacker with access to any signed saml document (by the IdP) can thus forge a SAML Response/Assertion with arbitrary contents. This would allow the attacker to log in as arbitrary user within the vulnerable system. This vulnerability is fixed in 1.17.0 and 1.12.3.

lib/omniauth/failure_endpoint.rb in OmniAuth before 1.9.2 (and before 2.0) does not escape the message_key value.

omniauth-apple is the OmniAuth strategy for "Sign In with Apple" (RubyGem omniauth-apple). In omniauth-apple before version 1.0.1 attackers can fake their email address during authentication. This vulnerability impacts applications using the omniauth-apple strategy of OmniAuth and using the info.email field of OmniAuth's Auth Hash Schema for any kind of identification. The value of this field may be set to any value of the attacker's choice including email addresses of other users. Applications not using info.email for identification but are instead using the uid field are not impacted in the same manner. Note, these applications may still be negatively affected if the value of info.email is being used for other purposes. Applications using affected versions of omniauth-apple are advised to upgrade to omniauth-apple version 1.0.1 or later.

The omniauth-weibo-oauth2 gem 0.4.6 for Ruby, as distributed on RubyGems.org, included a code-execution backdoor inserted by a third party. Versions through 0.4.5, and 0.5.1 and later, are unaffected.

RubyGem omniauth-facebook has an access token security vulnerability

The request phase of the OmniAuth Ruby gem (1.9.1 and earlier) is vulnerable to Cross-Site Request Forgery when used as part of the Ruby on Rails framework, allowing accounts to be connected without user intent, user interaction, or feedback to the user. This permits a secondary account to be able to sign into the web application as the primary account.

OmniAuth OmnitAuth-SAML 1.9.0 and earlier may incorrectly utilize the results of XML DOM traversal and canonicalization APIs in such a way that an attacker may be able to manipulate the SAML data without invalidating the cryptographic signature, allowing the attack to potentially bypass authentication to SAML service providers.

In strategy.rb in OmniAuth before 1.3.2, the authenticity_token value is improperly protected because POST (in addition to GET) parameters are stored in the session and become available in the environment of the callback phase.

Cross-site request forgery (CSRF) vulnerability in the omniauth-oauth2 gem 1.1.1 and earlier for Ruby allows remote attackers to hijack the authentication of users for requests that modify session state.