diff --git a/sys/vfs/procfs/procfs_fpregs.c b/sys/vfs/procfs/procfs_fpregs.c
--- a/sys/vfs/procfs/procfs_fpregs.c
+++ b/sys/vfs/procfs/procfs_fpregs.c
@@ -37,6 +37,7 @@
  */
 
 #include <sys/param.h>
+#include <sys/systm.h>
 #include <sys/uio.h>
 #include <sys/proc.h>
 #include <sys/caps.h>
@@ -53,6 +54,14 @@
 	int error;
 	struct fpreg r;
 
+	/*
+	 * Zero-initialize so that the regions of struct fpreg not populated
+	 * by fill_fpregs (sv_pad0/sv_pad in the save87 overlay, plus the
+	 * entire fpr_xacc+fpr_spare tail on the cpu_fxsr path) cannot leak
+	 * stale kernel-stack bytes to userspace via uiomove_frombuf below.
+	 */
+	bzero(&r, sizeof(r));
+
 	/* Can't trace a process that's currently exec'ing. */
 	if ((p->p_flags & P_INEXEC) != 0)
 		return EAGAIN;