network-manager-vpnc has been archived upstream which means that bug
reports, bug fixes, and translation updates are no longer accepted.

See the README at
https://gitlab.gnome.org/GNOME/NetworkManager-vpnc
or
https://blogs.gnome.org/mcatanzaro/2026/09/15/privilege-escalation-vulnerabilities-in-networkmanager-plugins/

Please consider whether this package should be removed from Debian.
The package has already been removed from Fedora.

The blog post suggested that this could be an alternative:
https://gitlab.gnome.org/GNOME/NetworkManager-libreswan

Thank you,
Jeremy Bícha