Arch Linux 2021 Advisory: ASA-202106-25 Moderate Severity Denial of Service

Arch Linux Security Advisory ASA-202106-25
=========================================
Severity: Medium
Date    : 2021-06-09
CVE-ID  : CVE-2021-33503
Package : python-urllib3
Type    : denial of service
Remote  : Yes
Link    : https://security.archlinux.org/AVG-2038

Summary
======
The package python-urllib3 before version 1.26.5-1 is vulnerable to
denial of service.

Resolution
=========
Upgrade to 1.26.5-1.

# pacman -Syu "python-urllib3>=1.26.5-1"

The problem has been fixed upstream in version 1.26.5.

Workaround
=========
None.

Description
==========
A security issue has been found in python-urllib3 before version
1.26.5. When provided with a URL containing many @ characters in the
authority component, the authority regular expression exhibits
catastrophic backtracking, causing a denial of service if a URL was
passed as a parameter or redirected to via an HTTP redirect.

Impact
=====
A remote attacker could exhaust CPU resources, leading to denial of
service, using a crafted URL.

References
=========
https://github.com/urllib3/urllib3/security/advisories/GHSA-q2q7-5pp4-w6pg
https://github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec
https://security.archlinux.org/CVE-2021-33503