CVE-2021-23336 (Moderate severity, published 2021-02-12)
CVSS score: 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:H)
CWE: CWE-444
Description: 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.
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.

Within regulated environments, a combination of the following controls acts as a significant barrier to successfully exploiting a CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability and therefore downgrades the severity of this particular CVE from Moderate to Low.

The platform uses secure, encrypted HTTPS connections over TLS 1.2 to reduce the risk of smuggling attacks by preventing the injection of ambiguous or malformed requests between components. The environment employs IPS/IDS and antimalware solutions to detect and block malicious code while ensuring consistent interpretation of HTTP requests across network layers, mitigating request/response inconsistencies. Event logs are collected and analyzed for centralization, correlation, monitoring, alerting, and retention, enabling the detection of malformed or suspicious HTTP traffic. Static code analysis and peer reviews enforce strong input validation and error handling to ensure all user inputs adhere to HTTP protocol specifications.