As part of our ongoing security efforts, a vulnerability was discovered that affects the way content is stored and retrieved within the Docker Engine. Today we are releasing a security update that addresses this issue in accordance with our coordinated responsible disclosure policy.
At push time, Docker’s layer IDs are currently randomly generated and assigned. An image intentionally created to have colliding layer IDs can override a subsequently pulled layer’s ID causing different content to run than intended. This vulnerability can only affect Docker Engine hosts where the user has been convinced into pulling a maliciously crafted image. The upgrade to Docker ensures that the content on disk matches the content of the layer being pulled, or a new non-colliding ID will be generated and assigned (a change only to the metadata).
In order to ensure user safety, we conducted a thorough audit of every image on Docker Hub, and found no evidence of malicious uses of conflicting layer IDs. We have also had no reports of exploits of this vulnerability. Nevertheless, we strongly recommend that users update to the new versions of Docker Engine.
We recommend that users upgrade to the latest version of Docker Engine. If you are unable to upgrade right away, only pull content from trusted sources. Additionally you can follow Docker security best practices (which includes only pulling from trusted sources) and audit your host configurations using Docker Bench.
Upgrade instructions and software downloads are available here:
You can expect our team to continue improving the security of Docker by not only shipping features such as Docker Content Trust and tools like Docker Bench, but also by continuing to be proactive in finding security vulnerabilities in our products.
To keep up to date on all the latest Docker Security news, make sure you check out our Security page, subscribe to our mailing list, or find us in #docker-security.
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