Medium [CVE-2021-3733] python: There's a flaw in urllib's AbstractBasicAuthHandler class
This medium-severity Red Hat Linux advisory covers CVE-2021-3733 affecting Red Hat Enterprise Linux 8, Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUS, Red Hat Enterprise Linux 6.
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Summary
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. Applications that use AbstractBasicAuthHandler, HTTPBasicAuthHandler and ProxyBasicAuthHandler may be affected by this flaw.
Other classes may use the vulnerable method http_error_auth_reqed in AbstractBasicAuthHandler as well. This flaw is out of support scope for versions of Python shipped in Red Hat Enterprise Linux 7 base OS and Red Hat Enterprise Linux 6.
For more information about support life cycles, please see Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H). Weakness: CWE-400.
Affected Red Hat products: Red Hat Enterprise Linux 8; Red Hat Software Collections for Red Hat Enterprise Linux 7; Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUS; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7. Will not fix / out of support: Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7.
Red Hat fixing advisory: RHSA-2021:4057, RHSA-2021:4160, RHSA-2022:1764, RHSA-2022:1821, RHSA-2021:3254, RHSA-2022:1663.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
- python3-0:3.6.8-39.el8_4
- python39:3.9-8050020210811100211.d428a79b
- python39-devel:3.9-8050020210811100211.d428a79b
- python38:3.8-8060020220120164031.5294be16
- python38-devel:3.8-8060020220120164031.5294be16
- python27:2.7-8060020220210185952.8cdc2268
- rh-python38-babel-0:2.7.0-12.el7
- rh-python38-python-0:3.8.11-2.el7
- rh-python38-python-cryptography-0:2.8-5.el7
- rh-python38-python-jinja2-0:2.10.3-6.el7
- rh-python38-python-lxml-0:4.4.1-7.el7
- rh-python38-python-pip-0:19.3.1-2.el7
- rh-python38-python-urllib3-0:1.25.7-7.el7
- python27-python-0:2.7.18-4.el7
- RHSA-2021:4057
- RHSA-2021:4160
- RHSA-2022:1764
- RHSA-2022:1821
- RHSA-2021:3254
- RHSA-2022:1663
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
Mitigation
Upgrade to a fixed release: python3-0:3.6.8-39.el8_4, python39:3.9-8050020210811100211.d428a79b, python39-devel:3.9-8050020210811100211.d428a79b, python38:3.8-8060020220120164031.5294be16, python38-devel:3.8-8060020220120164031.5294be16, python27:2.7-8060020220210185952.8cdc2268. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 6 days ago·verify at source
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