There's a flaw in urllib's AbstractBasicAuthHandler class. An attacker who controls a malicious HTTP server that an HTTP client (such as web browser) connects to, could trigger a Regular Expression Denial of Service (ReDOS) during an authentication request with a specially crafted payload that is sent by the server to the client. The greatest threat that this flaw poses is to application availability.
History

Mon, 03 Nov 2025 22:30:00 +0000

Type Values Removed Values Added
References

cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published: 2022-03-07T00:00:00.000Z

Updated: 2025-11-03T21:45:06.299Z

Reserved: 2021-08-23T00:00:00.000Z

Link: CVE-2021-3733

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Modified

Published: 2022-03-10T17:42:59.623

Modified: 2025-11-03T22:15:50.833

Link: CVE-2021-3733

cve-icon Redhat

Severity : Moderate

Publid Date: 2021-08-10T00:00:00Z

Links: CVE-2021-3733 - Bugzilla