CVE-2021-27020
📋 TL;DR
CVE-2021-27020 is a CSV injection vulnerability in Puppet Enterprise where user input wasn't properly sanitized during CSV export operations. This allows attackers to inject malicious formulas or commands that execute when the CSV file is opened in spreadsheet applications. Organizations running vulnerable Puppet Enterprise versions are affected.
💻 Affected Systems
- Puppet Enterprise
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution on client systems when malicious CSV files are opened in vulnerable spreadsheet applications, potentially leading to full system compromise.
Likely Case
Data exfiltration, phishing attacks, or local code execution on user workstations when CSV files are opened.
If Mitigated
Limited impact with proper user training about opening untrusted CSV files and application whitelisting.
🎯 Exploit Status
Exploitation requires authenticated access to Puppet Enterprise and user interaction to open CSV files.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2019.8.7, 2021.0.1, 2021.1.1, 2021.2.1, 2021.3.1, 2021.4.1 or later
Vendor Advisory: https://puppet.com/security/cve/CVE-2021-27020
Restart Required: Yes
Instructions:
1. Backup Puppet Enterprise configuration and data. 2. Download appropriate patch version from Puppet support portal. 3. Run upgrade installer following Puppet Enterprise upgrade documentation. 4. Verify services restart successfully.
🔧 Temporary Workarounds
Disable CSV Export
allRemove or restrict access to CSV export functionality in Puppet Enterprise
# Modify Puppet Enterprise configuration to disable CSV export endpoints
Input Validation
allImplement custom input validation for CSV export parameters
# Add input sanitization in Puppet Enterprise custom code
🧯 If You Can't Patch
- Restrict CSV export functionality to trusted users only
- Educate users to never open CSV files from untrusted sources in spreadsheet applications
🔍 How to Verify
Check if Vulnerable:
Check Puppet Enterprise version via command: puppet enterprise versionCheck Version:
puppet enterprise versionVerify Fix Applied:
Verify version is 2019.8.7, 2021.0.1, 2021.1.1, 2021.2.1, 2021.3.1, 2021.4.1 or later📡 Detection & Monitoring
Log Indicators:
- Unusual CSV export requests
- Large volume CSV exports
- Export requests with suspicious parameters
Network Indicators:
- CSV file downloads from Puppet Enterprise with formula injection patterns
SIEM Query:
source="puppet-enterprise" AND (event="csv_export" OR url_path="/csv") AND (user_agent="*excel*" OR user_agent="*libreoffice*")