CVE-2021-3733 - CVE House
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Status published Medium CVE-2021-3733

There's a flaw in urllib's AbstractBasicAuthHandler class. An attacker who...

Vulnerability Description

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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

No credits recorded in the NVD database.

Affected Vendor

Affected Software

python
Vulnerable Versions:
Fixed in python v3.6.14, python v3.7.11, python v3.8.10, python v3.9.5.

Timeline

Official Publish: March 7th, 2022
Last Modified: November 3rd, 2025
Added to House: July 21st, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weaknesses (CWE)