Vulnerability identifier: #VU25631

Vulnerability risk: Medium

CVSSv3.1: 4.2 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:L/E:P/RL:O/RC:C]

CVE-ID: CVE-2020-8492

CWE-ID: CWE-399

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Python
Universal components / Libraries / Scripting languages

Vendor: Python.org

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to improper input validation in urllib.request.AbstractBasicAuthHandler when processing HTTP responses. A remote attacker who controls a HTTP server can send a specially crafted HTTP response to the client application and conduct Regular Expression Denial of Service (ReDoS) attack.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Python: 3.8.0 - 3.8.2, 3.7.0 - 3.7.6, 3.6.0 - 3.6.10, 3.5.0 - 3.5.9, 2.7.0 - 2.7.2150

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External links
http://bugs.python.org/issue39503
http://github.com/python/cpython/pull/18284
http://python-security.readthedocs.io/vuln/urllib-basic-auth-regex.html
http://security.netapp.com/advisory/ntap-20200221-0001/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.