MEDIUM CVSS 5.9
Published: 2021-02-15

CVE-2021-23336

python python Security Advisory (CVE-2021-23336)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2021-23336 impacting python python. Evaluated with CVSS Base Score of 5.9 (MEDIUM).

Original NVD Description

Source: NIST NVD
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 v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
High (AC:H)
Depends on race conditions or environment
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
Required (UI:R)
User must click or open resource
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
Low (I:L)
Partial data modification possible
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product python / python
Affected Versions *
Weakness Enumeration CWE-444

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2021-23336 impacting python python.

⚡ Nuclei Detection Template (YAML) cve-2021-23336.yaml
id: cve-2021-23336

info:
  name: python python - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2021-23336 affecting python python.
    Evaluation: 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 vulner...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2021-23336
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:H
    cvss-score: 5.9
    cve-id: CVE-2021-23336
    cwe-id: CWE-444
  tags: cve,cve-2021-23336,python,python,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "python"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2021-23336.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2021-23336
# Target: python python | CVSS: 5.9 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2021-23336 (python python)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against python python scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2021-23336.sh
# Recommended Remediation & Patching Commands for CVE-2021-23336
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install python 2>/dev/null || \
sudo dnf upgrade python 2>/dev/null || \
sudo yum update python

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i python 2>/dev/null || rpm -qa | grep -i python

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2021-23336 in python python?

Review vendor-specific security notices and update python python packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2021-23336?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2021-23336?

CVE-2021-23336 is classified with a CVSS 3.1 Base Score of 5.9 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
5.9
MEDIUM SEVERITY
CVE ID CVE-2021-23336
Weakness CWE-444
Vendor python
Product python
Published 2021-02-15
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:H