CVE-2021-3733: ReDoS in urllib.request

The regular expression used by the AbstractBasicAuthHandler class of the urllib module is inefficient and can be abused by an attacker with a maliciuous HTTP server to cause a denial of service.


  • Disclosure date: 2021-01-30 (Python issue bpo-43075 reported)

Fixed In

Python issue

CVE-2021-3733: ReDoS in urllib.request.

  • Python issue: bpo-43075
  • Creation date: 2021-01-30
  • Reporter: yeting li


Timeline using the disclosure date 2021-01-30 as reference: