Debian Security Advisory

DLA-2628-1 python2.7 -- LTS security update

Date Reported:
17 Apr 2021
Affected Packages:
Security database references:
In Mitre's CVE dictionary: CVE-2019-16935, CVE-2021-23336.
More information:

Two security issues have been discovered in python2.7:

  • CVE-2019-16935

    The documentation XML-RPC server in Python 2.7 has XSS via the server_title field. This occurs in Lib/ in Python 2.x, and in Lib/xmlrpc/ in Python 3.x. If set_server_title is called with untrusted input, arbitrary JavaScript can be delivered to clients that visit the http URL for this server.

  • CVE-2021-23336

    The Python2.7 vulnerable to Web Cache Poisoning via urllib.parse.parse_qsl and urllib.parse.parse_qs by using a vector called parameter cloaking. When the attacker can separate query parameters using a semicolon (;), they can cause a difference in the interpretation of the request between the proxy (running with default configuration) and the server. This can result in malicious requests being cached as completely safe ones, as the proxy would usually not see the semicolon as a separator, and therefore would not include it in a cache key of an unkeyed parameter.

    **Attention, API-change!** Please be sure your software is working properly if it uses `urllib.parse.parse_qs` or `urllib.parse.parse_qsl`, `cgi.parse` or `cgi.parse_multipart`.

    Earlier Python versions allowed using both ``;`` and ``&`` as query parameter separators in `urllib.parse.parse_qs` and `urllib.parse.parse_qsl`. Due to security concerns, and to conform with newer W3C recommendations, this has been changed to allow only a single separator key, with ``&`` as the default. This change also affects `cgi.parse` and `cgi.parse_multipart` as they use the affected functions internally. For more details, please see their respective documentation.

    For Debian 9 stretch, these problems have been fixed in version 2.7.13-2+deb9u5.

    We recommend that you upgrade your python2.7 packages.

    For the detailed security status of python2.7 please refer to its security tracker page at:

    Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: