Sounds like the vulnerability is in the HTTP handling code, and because apt downloads packages over plain HTTP a man-in-the-middle position would be enough to exploit it.
It almost seems like a repeat of two previous apt vulnerabilities:
In 2019: https://lists.debian.org/debian-security-announce/2019/msg00...
And in 2014: https://lists.debian.org/debian-security-announce/2014/msg00...
Is there a German word for a broken tool that can only be fixed by using the same broken tool?
hiddenvulkcan•20m ago