CVE-2021-23336
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.
Statement
The python2.7 component in Red Hat Enterprise Linux 9 is listed as not affected as it was removed prior to the release of RHEL-9.0.
The python3.9 component in Red Hat Enterprise Linux 9 is listed as not affected as a patched version was verified in RHEL-9.0 beta and the RHEL-9.0 GA release included this patched version.
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert: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 Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.9 | 5.9 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | Required | Required | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | Low | Low | N/A |
| Availability Impact | High | High | N/A |
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
Understanding the Weakness (CWE)
Integrity,Non-Repudiation,Access Control
Technical Impact: Unexpected State; Hide Activities; Bypass Protection Mechanism
An attacker could create HTTP messages to exploit a number of weaknesses including 1) the message can trick the web server to associate a URL with another URL's webpage and caching the contents of the webpage (web cache poisoning attack), 2) the message can be structured to bypass the firewall protection mechanisms and gain unauthorized access to a web application, and 3) the message can invoke a script or a page that returns client credentials (similar to a Cross Site Scripting attack).
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