CVE-2012-6639
📋 TL;DR
CVE-2012-6639 is a privilege escalation vulnerability in Cloud-init versions before 0.7.0 that allows local attackers to gain root privileges by submitting malicious requests to an untrusted EC2 metadata service. This affects cloud instances using vulnerable Cloud-init versions to retrieve EC2 instance data. The vulnerability requires access to the local system but can lead to complete system compromise.
💻 Affected Systems
- Cloud-init
📦 What is this software?
Cloud Init by Canonical
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover with root privileges, allowing attacker to install persistent backdoors, exfiltrate sensitive data, pivot to other systems, and destroy or encrypt data.
Likely Case
Local privilege escalation to root, enabling installation of malware, credential theft, and lateral movement within the cloud environment.
If Mitigated
Limited impact with proper network segmentation and metadata service restrictions, potentially only allowing local user privilege escalation without network access.
🎯 Exploit Status
Exploitation requires local access to the system. The vulnerability is well-documented and proof-of-concept code exists in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Cloud-init 0.7.0 and later
Vendor Advisory: https://access.redhat.com/security/cve/cve-2012-6639
Restart Required: No
Instructions:
1. Update Cloud-init to version 0.7.0 or later using your distribution's package manager. 2. For Red Hat/CentOS: 'yum update cloud-init'. 3. For Ubuntu/Debian: 'apt-get update && apt-get install cloud-init'. 4. Verify the update completed successfully.
🔧 Temporary Workarounds
Restrict metadata service access
linuxConfigure iptables to block or restrict access to the EC2 metadata service (169.254.169.254) from local processes
iptables -A OUTPUT -d 169.254.169.254 -j DROP
iptables -A OUTPUT -d 169.254.169.254 -m owner --uid-owner root -j ACCEPT
Disable Cloud-init EC2 metadata
linuxConfigure Cloud-init to not use EC2 metadata service by modifying configuration files
echo 'datasource_list: [ None ]' > /etc/cloud/cloud.cfg.d/99-disable-ec2.cfg
🧯 If You Can't Patch
- Implement strict network controls to prevent access to EC2 metadata service (169.254.169.254)
- Apply principle of least privilege and monitor for privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check Cloud-init version: 'cloud-init --version' or 'dpkg -l | grep cloud-init' or 'rpm -q cloud-init'. If version is earlier than 0.7.0, system is vulnerable.Check Version:
cloud-init --version 2>/dev/null || dpkg -l cloud-init 2>/dev/null || rpm -q cloud-init 2>/dev/nullVerify Fix Applied:
Verify Cloud-init version is 0.7.0 or later: 'cloud-init --version' should show 0.7.0+. Test that Cloud-init still functions for legitimate initialization tasks.📡 Detection & Monitoring
Log Indicators:
- Unusual privilege escalation attempts in system logs
- Failed or unusual Cloud-init metadata requests
- Processes accessing EC2 metadata service with non-root privileges
Network Indicators:
- Local processes making requests to 169.254.169.254
- Unusual outbound connections from cloud instances to metadata service
SIEM Query:
source="*syslog*" AND ("privilege escalation" OR "setuid" OR "sudo") AND process="cloud-init"🔗 References
- http://www.openwall.com/lists/oss-security/2014/03/06/7
- https://access.redhat.com/security/cve/cve-2012-6639
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2012-6639
- https://bugzilla.suse.com/show_bug.cgi?id=CVE-2012-6639
- https://security-tracker.debian.org/tracker/CVE-2012-6639
- https://www.securityfocus.com/bid/66019/references
- http://www.openwall.com/lists/oss-security/2014/03/06/7
- https://access.redhat.com/security/cve/cve-2012-6639
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2012-6639
- https://bugzilla.suse.com/show_bug.cgi?id=CVE-2012-6639
- https://security-tracker.debian.org/tracker/CVE-2012-6639
- https://www.securityfocus.com/bid/66019/references
