CVE-2021-46822: Out-of-bounds Write

The PPM reader in libjpeg-turbo through 2.0.90 mishandles use of tjLoadImage for loading a 16-bit binary PPM file into a grayscale buffer and loading a 16-bit binary PGM file into an RGB buffer. This is related to a heap-based buffer overflow in the get_word_rgb_row function in rdppm.c.