The overlayfs implementation in the linux (aka Linux kernel) package before 3.19.0-21.21 in Ubuntu through 15.04 does not properly check permissions for file creation in the upper filesystem directory, which allows local users to obtain root access by leveraging a configuration in which overlayfs is permitted in an arbitrary mount namespace.
http://seclists.org/oss-sec/2015/q2/717
http://www.exploit-db.com/exploits/40688/
http://www.securityfocus.com/bid/75206
https://people.canonical.com/~ubuntu-security/cve/2015/CVE-2015-1328.html
Source: MITRE
Published: 2016-11-28
Updated: 2017-09-21
Type: CWE-264
Base Score: 7.2
Vector: AV:L/AC:L/Au:N/C:C/I:C/A:C
Impact Score: 10
Exploitability Score: 3.9
Severity: HIGH
Base Score: 7.8
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 1.8
Severity: HIGH