diff --git a/wolfcrypt/src/sp_int.c b/wolfcrypt/src/sp_int.c
index db84a3e72..763ec1f8f 100644
--- a/wolfcrypt/src/sp_int.c
+++ b/wolfcrypt/src/sp_int.c
@@ -7125,7 +7125,7 @@ int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
 #if (defined(WOLFSSL_SMALL_STACK) || defined(SP_ALLOC)) && \
     !defined(WOLFSSL_SP_NO_MALLOC)
         int cnt = 4;
-        if ((rem != NULL) && (rem != d)) {
+        if ((rem != NULL) && (rem != d) && (rem->size > a->used)) {
             cnt--;
         }
         if ((r != NULL) && (r != d)) {
@@ -7144,8 +7144,9 @@ int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
 #if (defined(WOLFSSL_SMALL_STACK) || defined(SP_ALLOC)) && \
     !defined(WOLFSSL_SP_NO_MALLOC)
         i = 2;
-        sa    = ((rem != NULL) && (rem != d)) ? rem : td[i++];
-        tr    = ((r != NULL) && (r != d))     ? r   : td[i];
+        sa    = ((rem != NULL) && (rem != d) && (rem->size > a->used)) ? rem :
+            td[i++];
+        tr    = ((r != NULL) && (r != d)) ? r : td[i];
 #else
         sa    = td[2];
         tr    = td[3];
@@ -7155,10 +7156,10 @@ int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
         sp_init_size(trial, a->used + 1);
 #if (defined(WOLFSSL_SMALL_STACK) || defined(SP_ALLOC)) && \
     !defined(WOLFSSL_SP_NO_MALLOC)
-        if ((rem == NULL) || (rem == d)) {
+        if (sa != rem) {
             sp_init_size(sa, a->used + 1);
         }
-        if ((r == NULL) || (r == d)) {
+        if (tr != r) {
             sp_init_size(tr, a->used - d->used + 2);
         }
 #else
@@ -11309,31 +11310,47 @@ int sp_exptmod_ex(sp_int* b, sp_int* e, int digits, sp_int* m, sp_int* r)
     }
 #endif
 
-    if (err != MP_OKAY) {
-    }
-    /* Handle special cases. */
-    else if (sp_iszero(m)) {
+    /* Check for invalid modulus. */
+    if ((err == MP_OKAY) && sp_iszero(m)) {
         err = MP_VAL;
     }
 #ifdef WOLFSSL_SP_INT_NEGATIVE
-    else if ((e->sign == MP_NEG) || (m->sign == MP_NEG)) {
+    /* Check for unsupported negative values of exponent and modulus. */
+    if ((err == MP_OKAY) && ((e->sign == MP_NEG) || (m->sign == MP_NEG))) {
         err = MP_VAL;
     }
 #endif
-    else if (sp_isone(m)) {
+
+    /* Check for degenerate cases. */
+    if ((err == MP_OKAY) && sp_isone(m)) {
         sp_set(r, 0);
         done = 1;
     }
-    else if (sp_iszero(e)) {
+    if ((!done) && (err == MP_OKAY) && sp_iszero(e)) {
         sp_set(r, 1);
         done = 1;
     }
-    else if (sp_iszero(b)) {
+
+    /* Check whether base needs to be reduced. */
+    if ((!done) && (err == MP_OKAY) && (_sp_cmp_abs(b, m) != MP_LT)) {
+        if ((r == e) || (r == m)) {
+            err = MP_VAL;
+        }
+        if (err == MP_OKAY) {
+            err = sp_mod(b, m, r);
+        }
+        if (err == MP_OKAY) {
+            b = r;
+        }
+    }
+    /* Check for degenerate case of base. */
+    if ((!done) && (err == MP_OKAY) && sp_iszero(b)) {
         sp_set(r, 0);
         done = 1;
     }
+
     /* Ensure SP integers have space for intermediate values. */
-    else if (m->used * 2 >= r->size) {
+    if ((!done) && (err == MP_OKAY) && (m->used * 2 >= r->size)) {
         err = MP_VAL;
     }