util.c in runV 1.0.0 for Docker mishandles a numeric username, which allows attackers to obtain root access by leveraging the presence of an initial numeric value on an /etc/passwd line, and then issuing a "docker exec" command with that value in the -u argument, a similar issue to CVE-2016-3697.

libcontainer/user/user.go in runC before 0.1.0, as used in Docker before 1.11.2, improperly treats a numeric UID as a potential username, which allows local users to gain privileges via a numeric username in the password file in a container.