CLSA-2026-1778602853 Fix CVE(s): CVE-2026-7598

SECURITY UPDATE: fix integer overflow in usernamelen bounds checks across userauthlist, userauthpassword and password change paths in src/userauth.c - debian/patches/CVE-2026-7598.patch: fix integer overflow in usernamelen bounds checks across userauthlist, userauthpassword and password change...