CVE-2021-42716

An issue was discovered in stb stb_image.h 2.27. The PNM loader incorrectly
interpreted 16-bit PGM files as 8-bit when converting to RGBA, leading to a
buffer overflow when later reinterpreting the result as a 16-bit buffer. An
attacker could potentially have crashed a service using stb_image, or read
up to 1024 bytes of non-consecutive heap data without control over the read
location.