It was found that various OpenID Providers (OPs) had TLS Server Certificates that used weak keys, as a result of the Debian Predictable Random Number Generator (CVE-2008-0166). In combination with the DNS Cache Poisoning issue (CVE-2008-1447) and the fact that almost all SSL/TLS implementations do not consult CRLs (currently an untracked issue), this means that it is impossible to rely on these OPs.

Ruby OpenID (aka ruby-openid) through 2.8.0 has a remotely exploitable flaw. This library is used by Rails web applications to integrate with OpenID Providers. Severity can range from medium to critical, depending on how a web application developer chose to employ the ruby-openid library. Developers who based their OpenID integration heavily on the "example app" provided by the project are at highest risk.

Doorkeeper::OpenidConnect (aka the OpenID Connect extension for Doorkeeper) 1.4.x and 1.5.x before 1.5.4 has an open redirect via the redirect_uri field in an OAuth authorization request (that results in an error response) with the 'openid' scope and a prompt=none value. This allows phishing attacks against the authorization flow.

message/ax/AxMessage.java in OpenID4Java before 0.9.6 final, as used in JBoss Enterprise Application Platform 5.1 before 5.1.2, Step2, Kay Framework before 1.0.2, and possibly other products does not verify that Attribute Exchange (AX) information is signed, which allows remote attackers to modify potentially sensitive AX information without detection via a man-in-the-middle (MITM) attack.

PHP remote file inclusion vulnerability in includes/openid/Auth/OpenID/BBStore.php in phpBB Openid 0.2.0 allows remote attackers to execute arbitrary PHP code via a URL in the openid_root_path parameter.

OpenID allows remote attackers to forcibly log a user into an OpenID enabled site, divulge the user's personal information to this site, and add it site to the trusted sites list via a crafted web page, related to cached tokens.

Cross-site request forgery (CSRF) vulnerability in OpenID allows remote attackers to restore the login session of a user on an OpenID enabled site via unspecified vectors related to an arbitrary remote web site and cached tokens, after the user has signed into an OpenID server, logged into the OpenID enabled site, and then logged out of the OpenID enabled site.