The Linux kernel through 3.17.4 does not properly restrict dropping of supplemental group memberships in certain namespace scenarios, which allows local users to bypass intended file permissions by leveraging a POSIX ACL containing an entry for the group category that is more restrictive than the entry for the other category, aka a “negative groups” issue, related to kernel/groups.c, kernel/uid16.c, and kernel/user_namespace.c.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-8989
Reference (s):
- BID:71154
- URL: http://www.securityfocus.com/bid/71154
- http://thread.gmane.org/gmane.linux.man/7385/
- FEDORA:FEDORA-2015-0515
- URL: http://lists.fedoraproject.org/pipermail/package-announce/2015-January/147973.html