Vulnerability identifier: #VU21440

Vulnerability risk: Medium

CVSSv3.1: 5.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N/E:P/RL:O/RC:C]

CVE-ID: CVE-2019-16935

CWE-ID: CWE-79

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 cross-site scripting (XSS) attacks.

The vulnerability exists due to insufficient sanitization of user-supplied data when processing the server_title field in the XML-RPC server (Lib/DocXMLRPCServer.py) in Python 2.x, and in Lib/xmlrpc/server.py in Python 3.x. A remote attacker can trick the victim to follow a specially crafted link and execute arbitrary HTML and script code in user's browser in context of vulnerable website.

Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Python: 2.7.0 - 2.7.16, 3.6 - 3.6.9, 3.7.0 - 3.7.4

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External links
http://bugs.python.org/issue38243
http://github.com/python/cpython/blob/35c0809158be7feae4c4f877a08b93baea2d8291/Lib/xmlrpc/server.py#L897
http://github.com/python/cpython/blob/e007860b8b3609ce0bc62b1780efaa06241520bd/Lib/DocXMLRPCServer.py#L213
http://github.com/python/cpython/pull/16373

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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.