The hash functionality in json-c before 0.12 allows context-dependent attackers to cause a denial of service (CPU consumption) via crafted JSON data, involving collisions.
https://github.com/json-c/json-c/commit/64e36901a0614bf64a19bc3396469c66dcd0b015
https://exchange.xforce.ibmcloud.com/vulnerabilities/92541
https://bugzilla.redhat.com/show_bug.cgi?id=1032311
http://www.securityfocus.com/bid/66715
http://www.oracle.com/technetwork/topics/security/bulletinoct2015-2511968.html
http://secunia.com/advisories/57791
http://lists.fedoraproject.org/pipermail/package-announce/2014-April/131845.html