Linux kernel built with the User Namespaces(CONFIG_USER_NS) support is vulnerable to a potential privilege escalation flaw. It could occur when a root owned process tries to enter a user namespace, wherein a user attempts to attach the entering process via ptrace(1). A privileged name space user could use this flaw to potentially escalate their privileges on the system. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-8709
