libevent -- integer overflow in evbuffers

Debian Security Team reports:

Andrew Bartlett of Catalyst reported a defect affecting certain
applications using the Libevent evbuffer API. This defect leaves
applications which pass insanely large inputs to evbuffers open
to a possible heap overflow or infinite loop. In order to exploit
this flaw, an attacker needs to be able to find a way to provoke
the program into trying to make a buffer chunk larger than what
will fit into a single size_t or off_t.