An issue was discovered in Django 5.1 before 5.1.5, 5.0 before 5.0.11, and 4.2 before 4.2.18. Lack of upper-bound limit enforcement in strings passed when performing IPv6 validation could lead to a potential denial-of-service attack. The undocumented and private functions clean_ipv6_address and is_valid_ipv6_address are vulnerable, as is the django.forms.GenericIPAddressField form field.

(The django.db.models.GenericIPAddressField model field is not affected.)