As the Docker container craze continues to gather pace, it’s a foregone conclusion that vulnerabilities in the technology will emerge.

Docker containers sprung their first major leak back in June when a quickly patched vulnerability was discovered that allowed rogue programs to break out of their containers and access files on the host operating system. Now there’s news of a new, even nastier vulnerability, which could allow attackers to gain elevated privileges and remotely execute code on affected systems.

Thankfully the Docker Inc. team has moved quickly to repair the bug once again, and the latest Docker 1.3.2 is immune. However all previous versions of the software remain vulnerable, according to the the company.

“No remediation is available for older versions of Docker and users are advised to upgrade,” Docker said in a statement on Monday.

Officially known as CVE-2014-6407, the vulnerability was discovered by Red Hat Inc’s Florian Weimer and security researcher Tõnis Tiigi. The flaw exploits the way Docker works with system image files. In older versions, Docker follows hard and symbolic image archiev links in blind fashion, which leaves them vulnerable to malicious images that can write files to arbitrary directories on disk. This has been fixed with the latest Docker 1.3.2, as the software now scans images before it extracts them, with the extraction process taking place inside a sandbox to ensure images only have limited access to the file system.

Monday’s security bulletin also described a second vulnerability inside Docker, called CVE-2014-6408, which only affects versions 1.3.0 and 1.3.1.

This flaw could potentially allow attackers to compromise the security restrictions applied to specific containers, as these older versions of the software accept and apply new security options from Docker images. Given the right circumstances, it could allow a malicious program to escape from its container and attack the host operating system.

In other words, Docker users should upgrade to the latest version ASAP if they want to avoid any troubles.

Docker version 1.3.2 is available to download on all supported platforms, with instructions for installation available here.

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