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.

CVSS 3.1

5.9CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:H

EPSS

41% chance of exploitation in the next 30 days; higher than 98% of CVEs (scores of 2026-10-25)

CWE

CWE-444

Published

2021-02-15

Modified

2026-10-14

Record from

the NVD, synced 2026-10-19

Affected

• debian:debian_linux
• djangoproject:django
• fedoraproject:fedora
• netapp:cloud_backup
• netapp:inventory_collect_tool
• netapp:ontap_select_deploy_administration_utility
• netapp:snapcenter
• oracle:communications_offline_mediation_controller
• oracle:communications_pricing_design_center
• oracle:enterprise_manager_ops_center
• oracle:zfs_storage_appliance
• python:python

References

• http://www.openwall.com/lists/oss-security/2021/02/19/4
• http://www.openwall.com/lists/oss-security/2021/05/01/2
• https://github.com/python/cpython/pull/24297
• https://lists.apache.org/thread.html/ra8ce70088ba291f358e077cafdb14d174b7a1ce9a9d86d1b332d6367%40%3Cusers.airflow.apache.org%3E
• https://lists.apache.org/thread.html/rc005f4de9d9b0ba943ceb8ff5a21a5c6ff8a9df52632476698d99432%40%3Cannounce.apache.org%3E

Check your stackJSON