Docker CopyEscape vulnerability allows host file overwrites

A critical vulnerability in Docker, identified as CVE-2026-17106 and dubbed ‘CopyEscape’, allows malicious containers to overwrite files on a host machine. The flaw occurs during the ‘docker cp’ command, specifically during copy-out operations where data is moved from a container to the host system.

Discovered by Imperva’s Red Team, the exploit leverages two primary weaknesses in the archive-processing path. First, a race condition allows an attacker to replace a directory with a symbolic link while Docker is scanning the filesystem. Second, the Docker CLI fails to consistently restrict filesystem operations to the intended destination, allowing crafted symlinks to point to locations outside the designated output directory. The severity of the impact depends on the privileges of the user executing the command.

This vulnerability highlights broader architectural concerns regarding container security. Unlike virtual machines, containers share the host operating system's kernel. This shared-kernel architecture means that while containers provide deployment and resource isolation, they do not offer a complete security boundary against kernel-level attacks, making them susceptible to escape techniques if vulnerabilities exist.