diff -up shadow-4.9/libmisc/prefix_flag.c.groupdel-fix-sigsegv-when-passwd-does-not-exist shadow-4.9/libmisc/prefix_flag.c

--- shadow-4.9/libmisc/prefix_flag.c.groupdel-fix-sigsegv-when-passwd-does-not-exist	2021-11-19 09:21:36.997091941 +0100

+++ shadow-4.9/libmisc/prefix_flag.c	2021-11-19 09:22:19.001341010 +0100

@@ -288,6 +288,9 @@ extern struct passwd* prefix_getpwent()

 	if(!passwd_db_file) {

 		return getpwent();

 	}

+	if (!fp_pwent) {

+		return NULL;

+	}

 	return fgetpwent(fp_pwent);

 }

 extern void prefix_endpwent()