The _asn1_check_identifier function in GNU Libtasn1 through 4.12 causes a NULL pointer dereference and crash when reading crafted input that triggers assignment of a NULL value within an asn1_node structure. It may lead to a remote denial of service attack.
https://www.debian.org/security/2018/dsa-4106
https://usn.ubuntu.com/3547-1/
https://security.gentoo.org/glsa/201710-11
https://lists.debian.org/debian-lts-announce/2020/06/msg00026.html