HTTP header injection via DomainNameValidator accepting newlines

Summary

An issue was discovered in Django 6.0 before 6.0.7 and 5.2 before 5.2.16. `DomainNameValidator` does not prohibit newlines in domain names (unless used via a form field, since `CharField` strips newlines). If an application uses values with newlines in an HTTP response, header injection can occur. Django itself is unaffected because `HttpResponse` prohibits newlines in HTTP headers. Earlier, unsupported Django series (such as 5.0.x, 4.1.x, and 3.2.x) were not evaluated and may also be affected. Django would like to thank Bence Nagy for reporting this issue. A flaw was found in Django. django.core.validators.DomainNameValidator accepted newline characters in domain name input. When applications use this validator outside Django form fields and include the validated value in HTTP response headers, a remote attacker could perform HTTP header injection. Django core is not affected because HttpResponse rejects newlines in headers, and CharField strips newlines by default. This flaw has a Low impact on Red Hat products. A vulnerability in Django's `DomainNameValidator` allows newline characters, which could enable HTTP header injection if validated values are directly used in HTTP response headers outside of Django's standard form handling.