CVE-2021-27017
📋 TL;DR
CVE-2021-27017 is a deserialization vulnerability in Puppet Agent that allows attackers to execute arbitrary code by supplying malicious serialized data. This affects Puppet Agent installations where untrusted data can be fed to vulnerable modules. Organizations using Puppet for configuration management are at risk.
💻 Affected Systems
- Puppet Agent
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the Puppet Agent service, potentially leading to complete system compromise and lateral movement across managed infrastructure.
Likely Case
Local privilege escalation or limited code execution within the Puppet Agent context, allowing attackers to manipulate configuration management and deploy malicious configurations.
If Mitigated
Limited impact due to network segmentation and strict input validation, potentially resulting in denial of service or failed exploitation attempts.
🎯 Exploit Status
Exploitation requires ability to inject malicious data into Puppet catalog processing, typically requiring some level of access to Puppet infrastructure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Puppet Agent 7.4.0 and later
Vendor Advisory: https://www.puppet.com/security/cve/cve-2021-27017-deserialization-untrusted-data
Restart Required: Yes
Instructions:
1. Backup Puppet configurations. 2. Upgrade Puppet Agent to version 7.4.0 or later using your package manager. 3. Restart Puppet Agent service. 4. Verify the upgrade was successful.
🔧 Temporary Workarounds
Input Validation Hardening
allImplement strict input validation for all data processed by Puppet modules to reject unexpected serialized data.
# Requires custom Puppet module development with input validation
Network Segmentation
allIsolate Puppet infrastructure from untrusted networks and implement strict firewall rules.
# Configure firewall to restrict Puppet traffic to trusted sources only
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Puppet infrastructure from potential attackers
- Monitor Puppet Agent logs for unusual deserialization attempts and implement alerting
🔍 How to Verify
Check if Vulnerable:
Check Puppet Agent version: if version is less than 7.4.0, the system is vulnerable.Check Version:
puppet --versionVerify Fix Applied:
Verify Puppet Agent version is 7.4.0 or higher and that the service is running normally after restart.📡 Detection & Monitoring
Log Indicators:
- Unusual deserialization errors in Puppet Agent logs
- Unexpected process execution from Puppet Agent context
Network Indicators:
- Unusual network connections originating from Puppet Agent
- Suspicious data payloads in Puppet communications
SIEM Query:
source="puppet-agent" AND ("deserialization" OR "untrusted data" OR "malformed catalog")