The fs_pin implementation in the Linux kernel before 4.0.5 does not ensure the internal consistency of a certain list data structure, which allows local users to cause a denial of service (system crash) by leveraging user-namespace root access for an MNT_DETACH umount2 system call, related to fs/fs_pin.c and include/linux/fs_pin.h.
http://openwall.com/lists/oss-security/2015/05/29/10
http://openwall.com/lists/oss-security/2015/05/29/5
http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.0.5
http://www.openwall.com/lists/oss-security/2015/06/04/5
https://bugzilla.redhat.com/show_bug.cgi?id=1249849
https://github.com/torvalds/linux/commit/820f9f147dcce2602eefd9b575bbbd9ea14f0953
Source: MITRE
Published: 2016-05-02
Updated: 2016-05-06
Type: NVD-CWE-Other
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:3.0/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