HIGH CVSS 8.8
Published: 2021-03-29

CVE-2021-27243

parallels parallels_desktop Security Advisory (CVE-2021-27243)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2021-27243 impacting parallels parallels_desktop. Evaluated with CVSS Base Score of 8.8 (HIGH).

Original NVD Description

Source: NIST NVD
This vulnerability allows local attackers to escalate privileges on affected installations of Parallels Desktop 16.0.1-48919. An attacker must first obtain the ability to execute low-privileged code on the target guest system in order to exploit this vulnerability. The specific flaw exists within the Toolgate component. The issue results from the lack of proper validation of user-supplied data, which can result in an integer overflow before allocating a buffer. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the hypervisor. Was ZDI-CAN-11924.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Local (AV:L)
Requires local system execution permissions
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
Low (PR:L)
Standard user access required
User Interaction
None (UI:N)
Zero human interaction required
Scope
Changed (S:C)
Impacts components beyond caller authority
Confidentiality
High (C:H)
Total information disclosure
Integrity
High (I:H)
Total modification of target system
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product parallels / parallels_desktop
Affected Versions 16.0.1
Weakness Enumeration CWE-190

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-2021-27243 impacting parallels parallels_desktop.

⚡ Nuclei Detection Template (YAML) cve-2021-27243.yaml
id: cve-2021-27243

info:
  name: parallels parallels_desktop - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2021-27243 affecting parallels parallels_desktop.
    Evaluation: This vulnerability allows local attackers to escalate privileges on affected installations of Parallels Desktop 16.0.1-48919. An attacker must first o...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2021-27243
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
    cvss-score: 8.8
    cve-id: CVE-2021-27243
    cwe-id: CWE-190
  tags: cve,cve-2021-27243,parallels,parallels_desktop,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "parallels_desktop"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2021-27243.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2021-27243
# Target: parallels parallels_desktop | CVSS: 8.8 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2021-27243 (parallels parallels_desktop)...")
    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 parallels parallels_desktop scope (16.0.1).")
        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-2021-27243.sh
# Recommended Remediation & Patching Commands for CVE-2021-27243
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install parallels_desktop 2>/dev/null || \
sudo dnf upgrade parallels_desktop 2>/dev/null || \
sudo yum update parallels_desktop

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

# 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.

🔗 Verified Technical References

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2021-27243 in parallels parallels_desktop?

Review vendor-specific security notices and update parallels parallels_desktop 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-2021-27243?

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-2021-27243?

CVE-2021-27243 is classified with a CVSS 3.1 Base Score of 8.8 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
8.8
HIGH SEVERITY
CVE ID CVE-2021-27243
Weakness CWE-190
Vendor parallels
Product parallels_desktop
Published 2021-03-29
Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H