CVE-2017-1000421

Gifsicle gifview 1.89 and older is vulnerable to a use-after-free in the read_gif function resulting potential code execution

CVE-2017-18120

A double-free bug in the read_gif function in gifread.c in gifsicle 1.90 allows a remote attacker to cause a denial-of-service attack or unspecified other impact via a maliciously crafted file, because last_name is mishandled, a different vulnerability than CVE-2017-1000421.