authentik has an insecure default configuration for OAuth2 Redirect URIs

Vulnerability Description

authentik is an open-source identity provider. Redirect URIs in the OAuth2 provider in authentik are checked by RegEx comparison. When no Redirect URIs are configured in a provider, authentik will automatically use the first redirect_uri value received as an allowed redirect URI, without escaping characters that have a special meaning in RegEx. Similarly, the documentation did not take this into consideration either. Given a provider with the Redirect URIs set to https://foo.example.com, an attacker can register a domain fooaexample.com, and it will correctly pass validation. authentik 2024.8.5 and 2024.10.3 fix this issue. As a workaround, When configuring OAuth2 providers, make sure to escape any wildcard characters that are not intended to function as a wildcard, for example replace `.` with `\.`.

References

• https://github.com/goauthentik/authentik/security/advisories/GHSA-3q5w-6m3x-64gj
• https://github.com/goauthentik/authentik/commit/85bb638243c8d7ea42ddd3b15b3f51a90d2b8c54