The keyctl_read_key function in security/keys/keyctl.c in the Linux kernel before 4.3.4 does not properly use a semaphore, which allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact via a crafted application that leverages a race condition between keyctl_revoke and keyctl_read calls.
http://lists.opensuse.org/opensuse-security-announce/2016-03/msg00094.html
http://lists.opensuse.org/opensuse-security-announce/2016-04/msg00045.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00038.html
http://www.debian.org/security/2016/dsa-3434
http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.3.4
http://www.securityfocus.com/bid/79903
http://www.ubuntu.com/usn/USN-2888-1
http://www.ubuntu.com/usn/USN-2890-1
http://www.ubuntu.com/usn/USN-2890-2
http://www.ubuntu.com/usn/USN-2890-3
http://www.ubuntu.com/usn/USN-2911-1
http://www.ubuntu.com/usn/USN-2911-2
https://bugzilla.redhat.com/show_bug.cgi?id=1291197
https://github.com/torvalds/linux/commit/b4a1b4f5047e4f54e194681125c74c0aa64d637d
Source: MITRE
Published: 2016-02-08
Updated: 2017-11-04
Type: CWE-362
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