REDHAT-BUG-2520658: High severity libevent libevent vulnerability

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has an incorrect integer conversion in eventtagging.c when evtagunmarshalheader uses evtagdecodeint to decode an attacker-controlled uint32 payload length and returns it as a signed int. Values above INTMAX become negative or truncated, and evtagunmarshalstring can use the converted value in allocation sizing, producing a wrapped large allocation request and denial of service. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.