Debian Security Advisory

DLA-2569-1 python-django -- LTS security update

Date Reported:
19 Feb 2021
Affected Packages:
Security database references:
In Mitre's CVE dictionary: CVE-2021-23336.
More information:

It was discovered that there was a web cache poisoning attack in Django, a popular Python-based web development framework.

This was caused by the unsafe handling of ";" characters in Python's urllib.parse.parse_qsl method which had been backported to Django's codebase to fix some other security issues in the past.

  • CVE-2021-23336

    The package python/cpython from 0 and before 3.6.13, from 3.7.0 and before 3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are 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.

For Debian 9 Stretch, these problems have been fixed in version 1:1.10.7-2+deb9u11.

We recommend that you upgrade your python-django packages.

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