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.
Severity
CVSS 3.1
9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
3.4% chance of exploitation in the next 30 days; higher than 88% of CVEs (scores of 2026-10-31)