I am uploading a NMU to fix this. Please find the debdiff attached.
diff -Nru libdumbnet-1.18.0/debian/changelog libdumbnet-1.18.0/debian/changelog
--- libdumbnet-1.18.0/debian/changelog 2024-03-10 12:11:12.000000000 +0000
+++ libdumbnet-1.18.0/debian/changelog 2024-05-26 16:35:47.000000000 +0000
@@ -1,3 +1,10 @@
+libdumbnet (1.18.0-1.1) unstable; urgency=medium
+
+ * Non-maintainer upload
+ * Drop strlcat/strlcpy from symbols (Closes: #1071321)
+
+ -- Bastian Germann <b...@debian.org> Sun, 26 May 2024 16:35:47 +0000
+
libdumbnet (1.18.0-1) unstable; urgency=medium
* [9f0ff73] New upstream version 1.18.0
diff -Nru libdumbnet-1.18.0/debian/libdumbnet1.symbols
libdumbnet-1.18.0/debian/libdumbnet1.symbols
--- libdumbnet-1.18.0/debian/libdumbnet1.symbols 2023-10-17
15:20:59.000000000 +0000
+++ libdumbnet-1.18.0/debian/libdumbnet1.symbols 2024-05-26
16:27:29.000000000 +0000
@@ -93,8 +93,6 @@
route_get@Base 1.8
route_loop@Base 1.8
route_open@Base 1.8
- strlcat@Base 1.8
- strlcpy@Base 1.8
tun_close@Base 1.11
tun_fileno@Base 1.11
tun_name@Base 1.11
