Django Allocation of Resources Without Limits or Throttling Vulnerability - CVE-2026-25673

An issue was discovered in 6.0 before 6.0.3 5.2 before 5.2.12 and 4.2 before 4.2.29. URLField.to_python() in Django calls urllib.parse.urlsplit() which performs NFKC normalization on Windows that is disproportionately slow for certain Unicode characters allowing a remote attacker to cause denial of service via large URL inputs containing these characters. 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 Seokchan Yoon for reporting this issue.