The example code for the digest authentication functionality (http_authentication.rb) in Ruby on Rails before 2.3.3 defines an authenticate_or_request_with_http_digest block that returns nil instead of false when the user does not exist, which allows context-dependent attackers to bypass authentication for applications that are derived from this example by sending an invalid username without a password.

References

• https://nvd.nist.gov/vuln/detail/CVE-2009-2422
• https://exchange.xforce.ibmcloud.com/vulnerabilities/51528
• http://lists.apple.com/archives/security-announce/2010//Mar/msg00001.html
• http://n8.tumblr.com/post/117477059/security-hole-found-in-rails-2-3s
• http://support.apple.com/kb/HT4077
• http://weblog.rubyonrails.org/2009/6/3/security-problem-with-authenticate_with_http_digest
• https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rails/CVE-2009-2422.yml
• https://web.archive.org/web/20090711160153/http://secunia.com/advisories/35702
• https://web.archive.org/web/20200229192617/http://www.securityfocus.com/bid/35579