CVE-2021-23336 - CVE House

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Status published Medium CVE-2021-23336

Web Cache Poisoning

5.9 CVSS

Vulnerability 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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

Snyk Security Team

References

More from n/a

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Affected Vendor

n/a

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Affected Software

python/cpython

Vulnerable Versions:

0, unspecified, 3.7.0, 3.8.0, 3.9.0

Timeline

Official Publish: February 15th, 2021

Last Modified: December 17th, 2025

Added to House: July 21st, 2026

CVSS Vectors

V3: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:H/E:P/RL:U/RC:C

Weaknesses (CWE)

No CWE data available

MITRE ATT&CK TTPs

No associated TTPs found for this vulnerability.