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 \..
Exploitability
AV:NAC:LAT:NPR:NUI:NVulnerable System
VC:NVI:NVA:NSubsequent System
SC:HSI:HSA:H7.9/CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:HOther