CVE-2021-3733

python: urllib: Regular expression DoS in AbstractBasicAuthHandler

Published Mar 7, 2022 CVSS 3.1 · 6.5 Medium EPSS 4.8% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-2808-1 python3.5 security update
Debian DLA Debian DLA DLA-3432-1 python2.7 security update
Debian DLA Debian DLA DLA-3477-1 python3.7 security update
Debian DLA Debian DLA DLA-3980-1 python3.9 security update
EUVD EUVD EUVD-2021-27010 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.
Ubuntu USN Ubuntu USN USN-5083-1 Python vulnerabilities
Ubuntu USN Ubuntu USN USN-5199-1 Python vulnerabilities
Ubuntu USN Ubuntu USN USN-5200-1 Python vulnerabilities
Ubuntu USN Ubuntu USN USN-6891-1 Python vulnerabilities
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
redhat
Published
Updated
Oct 14, 2026, 9:49 AM
Reserved
Aug 23, 2021, 12:00 AM
Status
Modified
Published
Mar 10, 2022, 5:42 PM
Modified
Oct 14, 2026, 10:17 AM
Severity
Moderate
Public date
Aug 10, 2021, 12:00 AM