An issue was discovered in Pillow before 8.1.1. In TiffDecode.c, there is a negative-offset memcpy with an invalid size.
https://security.gentoo.org/glsa/202107-33
https://pillow.readthedocs.io/en/stable/releasenotes/8.1.1.html
https://lists.debian.org/debian-lts-announce/2021/07/msg00018.html