Apache CXF’s OIDC relying-party component could redirect users to an attacker-controlled URL after successful authentication. The issue occurs because attacker-controlled state parameters are preserved and later used as redirect targets without validating that the final decoded URI belongs to the RP’s origin. Both directly encoded and double-encoded external URLs can trigger the issue, depending on which validation path is used. Users are recommended to upgrade to versions 4.2.4 or 4.1.9 or 3.6.13, which fix this issue.