In OpenBSD 7.3 before errata 016, npppd(8) could crash by a l2tp message which has an AVP (Attribute-Value Pair) with wrong length.
In OpenBSD 7.4 before errata 002 and OpenBSD 7.3 before errata 019, a network buffer that had to be split at certain length that could crash the kernel after receiving specially crafted escape sequences.