Apply by doing:
       cd /usr/src
       patch -p0 < 007_cd9660.patch

And then rebuild your kernel.

Index: sys/isofs/cd9660/cd9660_extern.h
===================================================================
RCS file: /cvs/src/sys/isofs/cd9660/cd9660_extern.h,v
retrieving revision 1.4
retrieving revision 1.5
diff -u -r1.4 -r1.5
--- sys/isofs/cd9660/cd9660_extern.h    2000/02/07 04:57:15     1.4
+++ sys/isofs/cd9660/cd9660_extern.h    2000/06/07 23:25:08     1.5
@@ -84,8 +84,8 @@
#define lblkno(imp, loc)       ((loc) >> (imp)->im_bshift)
#define blksize(imp, ip, lbn)  ((imp)->logical_block_size)

-int cd9660_mount __P((struct mount *,
-           const char *, caddr_t, struct nameidata *, struct proc *));
+int cd9660_mount __P((struct mount *, const char *, caddr_t,
+                      struct nameidata *, struct proc *));
int cd9660_start __P((struct mount *, int, struct proc *));
int cd9660_unmount __P((struct mount *, int, struct proc *));
int cd9660_root __P((struct mount *, struct vnode **));
@@ -96,6 +96,8 @@
int cd9660_fhtovp __P((struct mount *, struct fid *, struct vnode **));
int cd9660_vptofh __P((struct vnode *, struct fid *));
int cd9660_init __P((struct vfsconf *));
+int cd9660_check_export __P((struct mount *, struct mbuf *, int *,
+                             struct ucred **));
#define cd9660_sysctl ((int (*) __P((int *, u_int, void *, size_t *, void *, \
                                    size_t, struct proc *)))eopnotsupp)

Index: sys/isofs/cd9660/cd9660_vfsops.c
===================================================================
RCS file: /cvs/src/sys/isofs/cd9660/cd9660_vfsops.c,v
retrieving revision 1.19
retrieving revision 1.20
diff -u -r1.19 -r1.20
--- sys/isofs/cd9660/cd9660_vfsops.c    2000/02/07 04:57:15     1.19
+++ sys/isofs/cd9660/cd9660_vfsops.c    2000/06/07 23:25:08     1.20
@@ -77,7 +77,8 @@
       cd9660_fhtovp,
       cd9660_vptofh,
       cd9660_init,
-       cd9660_sysctl
+       cd9660_sysctl,
+       cd9660_check_export
};

/*
@@ -962,5 +963,31 @@
       printf("vptofh: ino %d, start %ld\n",
           ifhp->ifid_ino,ifhp->ifid_start);
#endif
+       return (0);
+}
+
+/*
+ * Verify a remote client has export rights and return these rights via
+ * exflagsp and credanonp.
+ */
+int
+cd9660_check_export(mp, nam, exflagsp, credanonp)
+       register struct mount *mp;
+       struct mbuf *nam;
+       int *exflagsp;
+       struct ucred **credanonp;
+{
+       register struct netcred *np;
+       register struct iso_mnt *imp = VFSTOISOFS(mp);
+
+       /*
+        * Get the export permission structure for this <mp, client> tuple.
+        */
+       np = vfs_export_lookup(mp, &imp->im_export, nam);
+       if (np == NULL)
+               return (EACCES);
+
+       *exflagsp = np->netc_exflags;
+       *credanonp = &np->netc_anon;
       return (0);
}