Double free() call on same memory chunk causes heap corruption with potential code execution.
vulners.com/securityvulns/securityvulns:doc:18228
vulners.com/securityvulns/securityvulns:doc:2621
vulners.com/securityvulns/securityvulns:doc:2626
vulners.com/securityvulns/securityvulns:doc:2719