The do_umount function in fs/namespace.c in the Linux kernel through 3.17 does not require the CAP_SYS_ADMIN capability for do_remount_sb calls that change the root filesystem to read-only, which allows local users to cause a denial of service (loss of writability) by making certain unshare system calls, clearing the / MNT_LOCKED flag, and making an MNT_FORCE umount system call.
http://secunia.com/advisories/60174
http://secunia.com/advisories/61145
http://secunia.com/advisories/62633
http://secunia.com/advisories/62634
http://thread.gmane.org/gmane.linux.kernel.stable/109312
http://www.openwall.com/lists/oss-security/2014/10/08/22
http://www.securityfocus.com/bid/70314
http://www.securitytracker.com/id/1031180
http://www.ubuntu.com/usn/USN-2415-1
http://www.ubuntu.com/usn/USN-2416-1
http://www.ubuntu.com/usn/USN-2417-1
http://www.ubuntu.com/usn/USN-2418-1
http://www.ubuntu.com/usn/USN-2419-1
http://www.ubuntu.com/usn/USN-2420-1
http://www.ubuntu.com/usn/USN-2421-1
https://access.redhat.com/errata/RHSA-2017:1842
https://access.redhat.com/errata/RHSA-2017:2077
Source: MITRE
Published: 2014-10-13
Updated: 2020-08-14
Type: NVD-CWE-noinfo
Base Score: 4.9
Vector: AV:L/AC:L/Au:N/C:N/I:N/A:C
Impact Score: 6.9
Exploitability Score: 3.9
Severity: MEDIUM
Base Score: 5.5
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Impact Score: 3.6
Exploitability Score: 1.8
Severity: MEDIUM