The KEYS subsystem in the Linux kernel before 4.4 allows local users to gain privileges or cause a denial of service (BUG) via crafted keyctl commands that negatively instantiate a key, related to security/keys/encrypted-keys/encrypted.c, security/keys/trusted.c, and security/keys/user_defined.c. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-8539
