Facebook Google Plus Twitter LinkedIn YouTube RSS Menu Search Resource - BlogResource - WebinarResource - ReportResource - Eventicons_066 icons_067icons_068icons_069icons_070

AWS EC2 macOS Local Privilege Escalation

Medium

Synopsis

We have discovered two avenues of local privilege escalation for AWS macOS EC2 instances. On macOS, Launch Daemons that are spawned from configurations specified within "/Library/LaunchDaemons/" are run with root privileges. By default, macOS EC2 instances have the following Launch Daemon configurations:

[email protected]-mini ~ % ls -1 /Library/LaunchDaemons
com.amazon.aws.ssm.plist
com.amazon.ec2.ena-ethernet.plist
com.amazon.ec2.macos-init.plist
com.amazon.ec2.monitoring.agents.cpuutilization.plist

Of these, com.amazon.ec2.macos-init.plist and com.amazon.ec2.monitoring.agents.cpuutilization.plist point to the following executables:

[email protected]-mini ~ % ls -al /usr/local/Cellar/ec2-macos-init/1.4.1/bin/ec2-macos-init
-r-xr-xr-x 1 ec2-user admin 6874432 Mar 15 20:23 /usr/local/Cellar/ec2-macos-init/1.4.1/bin/ec2-macos-init

[email protected]-mini ~ % ls -al /usr/local/Cellar/ec2-macos-system-monitor/1.2.0/libexec/bin/send-cpu-utilization
-rwxr-xr-x 1 ec2-user admin 2815880 Mar 2 00:22 /usr/local/Cellar/ec2-macos-system-monitor/1.2.0/libexec/bin/send-cpu-utilization

As can be seen above, the file owners of the above executables are ec2-user. This allows ec2-user to modify these files without restriction, such as swapping the binaries with something malicious, and have it executed as root the next time launchd spawns the corresponding the LaunchDaemon. This effectively allows for a privilege escalation from ec2-user to root.

To note, we are fully aware that this is not a "real" security issue. By default, ec2-user has sudo access and can already operate with root permissions whenever they please. In cases where the macOS EC2 instance is shared and has been configured to restrict sudo privileges, this could be a potential avenue for bypass. Obviously in such a case, admins could easily re-configure things and apply relevant permissions and mitigations themselves. We do, however, believe it'd be good to align with the permissions used for the binaries related to the other Launch Daemons (amazon-ena-ethernet and amazon-ssm-agent) by changing ownership of the binaries being used by ec2-macos-init and ec2-macos-system-monitor to root rather than the current ec2-user. Amazon has modified these permissions in the latest available AMIs.

Solution

Updated to latest AMI revision available.

Disclosure Timeline

April 13, 2021 - Tenable discloses to vendor.
April 13, 2021 - Vendor acknowledges receipt.
April 21, 2021 - Vendor sends status update that issue is still being investigated.
April 27, 2021 - Vendor sends status update that issue is still being investigated.
April 30, 2021 - Vendor states that fixes are in progress. Tenable acknowledges.
May 7, 2021 - Vendor sends status update that issue is still being investigated.
May 14, 2021 - Vendor sends status update that issue is still being investigated.
May 21, 2021 - Vendor states that fixes should be complete by 5/28. A coordinated disclosure will occur in next AMI release cycle.
June 10, 2021 - Vendor sends status update and states that fix is still on track to be released in June AMI release cycle.
June 30, 2021 - Tenable requests status update.
July 7, 2021 - Vendor states that updates are ready to be pushed.
July 7, 2021 - Tenable requests information about planned publication.

All information within TRA advisories is provided “as is”, without warranty of any kind, including the implied warranties of merchantability and fitness for a particular purpose, and with no guarantee of completeness, accuracy, or timeliness. Individuals and organizations are responsible for assessing the impact of any actual or potential security vulnerability.

Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

Try for Free Buy Now
Tenable.io FREE FOR 30 DAYS

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Sign up now.

Tenable.io BUY

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Purchase your annual subscription today.

65 assets

Choose Your Subscription Option:

Buy Now
Try for Free Buy Now

Try Nessus Professional Free

FREE FOR 7 DAYS

Nessus® is the most comprehensive vulnerability scanner on the market today. Nessus Professional will help automate the vulnerability scanning process, save time in your compliance cycles and allow you to engage your IT team.

Buy Nessus Professional

Nessus® is the most comprehensive vulnerability scanner on the market today. Nessus Professional will help automate the vulnerability scanning process, save time in your compliance cycles and allow you to engage your IT team.

Buy a multi-year license and save. Add Advanced Support for access to phone, community and chat support 24 hours a day, 365 days a year. Full details here.

Try for Free Buy Now

Try Tenable.io Web Application Scanning

FREE FOR 30 DAYS

Enjoy full access to our latest web application scanning offering designed for modern applications as part of the Tenable.io platform. Safely scan your entire online portfolio for vulnerabilities with a high degree of accuracy without heavy manual effort or disruption to critical web applications. Sign up now.

Buy Tenable.io Web Application Scanning

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Purchase your annual subscription today.

5 FQDNs

$3,578

Buy Now

Try for Free Contact Sales

Try Tenable.io Container Security

FREE FOR 30 DAYS

Enjoy full access to the only container security offering integrated into a vulnerability management platform. Monitor container images for vulnerabilities, malware and policy violations. Integrate with continuous integration and continuous deployment (CI/CD) systems to support DevOps practices, strengthen security and support enterprise policy compliance.

Buy Tenable.io Container Security

Tenable.io Container Security seamlessly and securely enables DevOps processes by providing visibility into the security of container images – including vulnerabilities, malware and policy violations – through integration with the build process.

Try for Free Contact Sales

Try Tenable Lumin

FREE FOR 30 DAYS

Visualize and explore your Cyber Exposure, track risk reduction over time and benchmark against your peers with Tenable Lumin.

Buy Tenable Lumin

Contact a Sales Representative to see how Lumin can help you gain insight across your entire organization and manage cyber risk.