CVE-2021-23336

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Description

The package python/cpython is 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.

The package python/cpython is 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.

Statement

The python36 component in the python36:3.6 module in Red Hat Enterprise Linux 8 is listed as not affected, as it does not contain Python interpreter or libraries. Packages of the python36 component only provide convenient links to the Python interpreter included in the non-modular python3 component's platform-python packages. Users of python36:3.6 module also need to check the entry for the python3 component to determine if their systems are affected. Red Hat Ceph Storage (RHCS) 3 ships an older version of python-django without the directly affected function, but which is still vulnerable to a similar attack involving the semi colon separator. Hence, impact has been rated as Low. Although Red Hat OpenStack Platform 13 & 16.1 both ship the affected code, since the proxy is controlled and configured by OpenStack, the impact has been lowered to Low. As a fix would require a substantial effort or commitment of time, no fix will be provided at this time.

The python36 component in the python36:3.6 module in Red Hat Enterprise Linux 8 is listed as not affected, as it does not contain Python interpreter or libraries. Packages of the python36 component only provide convenient links to the Python interpreter included in the non-modular python3 component's platform-python packages. Users of python36:3.6 module also need to check the entry for the python3 component to determine if their systems are affected.

Red Hat Ceph Storage (RHCS) 3 ships an older version of python-django without the directly affected function, but which is still vulnerable to a similar attack involving the semi colon separator. Hence, impact has been rated as Low.

Although Red Hat OpenStack Platform 13 & 16.1 both ship the affected code, since the proxy is controlled and configured by OpenStack, the impact has been lowered to Low. As a fix would require a substantial effort or commitment of time, no fix will be provided at this time.

Additional information

  • Bugzilla 1928904: python: Web cache poisoning via urllib.parse.parse_qsl and urllib.parse.parse_qs by using a semicolon in query parameters
  • CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
  • FAQ: Frequently asked questions about CVE-2021-23336

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).

CVSS v3 Score Breakdown
Red HatNVD

CVSS v3 Base Score

5.9

5.9

Attack Vector

Network

Network

Attack Complexity

High

High

Privileges Required

None

None

User Interaction

Required

Required

Scope

Unchanged

Unchanged

Confidentiality Impact

None

None

Integrity Impact

Low

Low

Availability Impact

High

High

CVSS v3 Vector

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

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

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?

What can I do if my product is listed as "Will not fix"?

What can I do if my product is listed as "Fix deferred"?

What is a mitigation?

I have a Red Hat product but it is not in the above list, is it affected?

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

My product is listed as "Out of Support Scope". What does this mean?

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