I am uploading a NMU to DELAYED/10 in order to fix this.
diff -Nru cdde-0.3.1/debian/changelog cdde-0.3.1/debian/changelog
--- cdde-0.3.1/debian/changelog 2023-10-03 20:14:51.000000000 +0200
+++ cdde-0.3.1/debian/changelog 2023-10-03 20:09:10.000000000 +0200
@@ -1,3 +1,11 @@
+cdde (0.3.1-1.1) unstable; urgency=medium
+
+ * Non-maintainer upload.
+ * Convert to source format 3.0 (Closes: #1007437).
+ * Fix FTBFS on hurd (Closes: #647965).
+
+ -- Bastian Germann <b...@debian.org> Tue, 03 Oct 2023 20:09:10 +0200
+
cdde (0.3.1-1) unstable; urgency=low
* Initial release (Closes: #493593).
diff -Nru cdde-0.3.1/debian/patches/hurd.patch
cdde-0.3.1/debian/patches/hurd.patch
--- cdde-0.3.1/debian/patches/hurd.patch 1970-01-01 01:00:00.000000000
+0100
+++ cdde-0.3.1/debian/patches/hurd.patch 2023-10-03 20:09:10.000000000
+0200
@@ -0,0 +1,16 @@
+diff -ur cdde-0.3.1.orig/src/cdde.c cdde-0.3.1/src/cdde.c
+--- cdde-0.3.1.orig/src/cdde.c 2008-08-25 15:33:49.000000000 +0200
++++ cdde-0.3.1/src/cdde.c 2011-11-08 01:55:13.000000000 +0100
+@@ -41,7 +41,12 @@
+ #include <stdlib.h>
+ #include <string.h>
+ #include <limits.h>
++#ifdef __linux__
+ #include <linux/cdrom.h>
++#endif
++#ifdef __GNU__
++#include <sys/cdrom.h>
++#endif
+ #include <fstab.h>
+ #include <signal.h>
+ #include <errno.h>
diff -Nru cdde-0.3.1/debian/patches/series cdde-0.3.1/debian/patches/series
--- cdde-0.3.1/debian/patches/series 1970-01-01 01:00:00.000000000 +0100
+++ cdde-0.3.1/debian/patches/series 2023-10-03 20:09:10.000000000 +0200
@@ -0,0 +1 @@
+hurd.patch
diff -Nru cdde-0.3.1/debian/source/format cdde-0.3.1/debian/source/format
--- cdde-0.3.1/debian/source/format 1970-01-01 01:00:00.000000000 +0100
+++ cdde-0.3.1/debian/source/format 2023-10-03 20:09:10.000000000 +0200
@@ -0,0 +1 @@
+3.0 (quilt)
