diff --git a/wolfcrypt/src/sha256.c b/wolfcrypt/src/sha256.c
index d891d647d..313082215 100644
--- a/wolfcrypt/src/sha256.c
+++ b/wolfcrypt/src/sha256.c
@@ -394,7 +394,10 @@ static int InitSha256(wc_Sha256* sha256)
         sha256->devCtx = NULL;
     #endif
     #ifdef WOLFSSL_SMALL_STACK_CACHE
-        sha256->W = NULL;
+        sha256->W = (word32*)XMALLOC(sizeof(word32) * WC_SHA256_BLOCK_SIZE,
+                                     sha256->heap, DYNAMIC_TYPE_DIGEST);
+        if (sha256->W == NULL)
+            return MEMORY_E;
     #endif
 
         ret = InitSha256(sha256);
@@ -772,7 +775,10 @@ static int InitSha256(wc_Sha256* sha256)
         sha256->devCtx = NULL;
     #endif
     #ifdef WOLFSSL_SMALL_STACK_CACHE
-        sha256->W = NULL;
+        sha256->W = (word32*)XMALLOC(sizeof(word32) * WC_SHA256_BLOCK_SIZE,
+                                     sha256->heap, DYNAMIC_TYPE_DIGEST);
+        if (sha256->W == NULL)
+            return MEMORY_E;
     #endif
 
         ret = InitSha256(sha256);
@@ -854,13 +860,8 @@ static int InitSha256(wc_Sha256* sha256)
 
     #ifdef WOLFSSL_SMALL_STACK_CACHE
         word32* W = sha256->W;
-        if (W == NULL) {
-            W = (word32*)XMALLOC(sizeof(word32) * WC_SHA256_BLOCK_SIZE, NULL,
-                                                           DYNAMIC_TYPE_DIGEST);
-            if (W == NULL)
-                return MEMORY_E;
-            sha256->W = W;
-        }
+        if (W == NULL)
+            return BAD_FUNC_ARG;
     #elif defined(WOLFSSL_SMALL_STACK)
         word32* W;
         W = (word32*)XMALLOC(sizeof(word32) * WC_SHA256_BLOCK_SIZE, NULL,
@@ -1465,6 +1466,15 @@ static int InitSha256(wc_Sha256* sha256)
             return BAD_FUNC_ARG;
         }
 
+#ifdef WOLFSSL_SMALL_STACK_CACHE
+    if (sha224->W == NULL) {
+        sha224->W = (word32*)XMALLOC(sizeof(word32) * WC_SHA256_BLOCK_SIZE,
+                                     sha224->heap, DYNAMIC_TYPE_DIGEST);
+        if (sha224->W == NULL)
+            return MEMORY_E;
+    }
+#endif
+
         sha224->digest[0] = 0xc1059ed8;
         sha224->digest[1] = 0x367cd507;
         sha224->digest[2] = 0x3070dd17;
@@ -1690,7 +1700,12 @@ void wc_Sha256Free(wc_Sha256* sha256)
 
         XMEMCPY(dst, src, sizeof(wc_Sha224));
     #ifdef WOLFSSL_SMALL_STACK_CACHE
-        dst->W = NULL;
+        dst->W = (word32*)XMALLOC(sizeof(word32) * WC_SHA256_BLOCK_SIZE,
+                                  dst->heap, DYNAMIC_TYPE_DIGEST);
+        if (dst->W == NULL) {
+            XMEMSET(dst, 0, sizeof(wc_Sha224));
+            return MEMORY_E;
+        }
     #endif
 
     #ifdef WOLFSSL_SILABS_SE_ACCEL
@@ -1787,7 +1802,12 @@ int wc_Sha256Copy(wc_Sha256* src, wc_Sha256* dst)
 
     XMEMCPY(dst, src, sizeof(wc_Sha256));
 #ifdef WOLFSSL_SMALL_STACK_CACHE
-    dst->W = NULL;
+    dst->W = (word32*)XMALLOC(sizeof(word32) * WC_SHA256_BLOCK_SIZE,
+                              dst->heap, DYNAMIC_TYPE_DIGEST);
+    if (dst->W == NULL) {
+        XMEMSET(dst, 0, sizeof(wc_Sha256));
+        return MEMORY_E;
+    }
 #endif
 
 #ifdef WOLFSSL_SILABS_SE_ACCEL
diff --git a/wolfcrypt/src/sha512.c b/wolfcrypt/src/sha512.c
index 88e9bf96a..5966f2c9c 100644
--- a/wolfcrypt/src/sha512.c
+++ b/wolfcrypt/src/sha512.c
@@ -582,7 +582,10 @@ static int InitSha512_Family(wc_Sha512* sha512, void* heap, int devId,
 
     sha512->heap = heap;
 #ifdef WOLFSSL_SMALL_STACK_CACHE
-    sha512->W = NULL;
+    sha512->W = (word64 *)XMALLOC((sizeof(word64) * 16) + WC_SHA512_BLOCK_SIZE,
+                                  sha512->heap, DYNAMIC_TYPE_DIGEST);
+    if (sha512->W == NULL)
+        return MEMORY_E;
 #endif
 #ifdef WOLF_CRYPTO_CB
     sha512->devId = devId;
@@ -714,14 +717,10 @@ static int _Transform_Sha512(wc_Sha512* sha512)
     word32 j;
     word64 T[8];
 
-#ifdef WOLFSSL_SMALL_STACK_CACHE
+#if defined(WOLFSSL_SMALL_STACK_CACHE)
     word64* W = sha512->W;
-    if (W == NULL) {
-        W = (word64*)XMALLOC(sizeof(word64) * 16, sha512->heap, DYNAMIC_TYPE_TMP_BUFFER);
-        if (W == NULL)
-            return MEMORY_E;
-        sha512->W = W;
-    }
+    if (W == NULL)
+        return BAD_FUNC_ARG;
 #elif defined(WOLFSSL_SMALL_STACK)
     word64* W;
     W = (word64*) XMALLOC(sizeof(word64) * 16, sha512->heap, DYNAMIC_TYPE_TMP_BUFFER);
@@ -1146,6 +1145,7 @@ void wc_Sha512Free(wc_Sha512* sha512)
 
 #ifdef WOLFSSL_SMALL_STACK_CACHE
     if (sha512->W != NULL) {
+        ForceZero(sha512->W, (sizeof(word64) * 16) + WC_SHA512_BLOCK_SIZE);
         XFREE(sha512->W, sha512->heap, DYNAMIC_TYPE_TMP_BUFFER);
         sha512->W = NULL;
     }
@@ -1168,10 +1168,16 @@ int wc_Sha512Transform(wc_Sha512* sha, const unsigned char* data)
 {
     int ret;
     /* back up buffer */
-#ifdef WOLFSSL_SMALL_STACK
-    word64 *buffer;
-#else
-    word64  buffer[WC_SHA512_BLOCK_SIZE  / sizeof(word64)];
+    WC_DECLARE_VAR(buffer, word64, WC_SHA512_BLOCK_SIZE  / sizeof(word64), 0);
+#if defined(WOLFSSL_SMALL_STACK_CACHE)
+    if (sha->W == NULL)
+        return BAD_FUNC_ARG;
+    buffer = sha->W + 16;
+#elif defined(WOLFSSL_SMALL_STACK)
+    word64 *buffer = (word64*)XMALLOC(WC_SHA512_BLOCK_SIZE, sha->heap,
+         DYNAMIC_TYPE_TMP_BUFFER);
+    if (buffer == NULL)
+        return MEMORY_E;
 #endif
 
     /* sanity check */
@@ -1179,13 +1185,6 @@ int wc_Sha512Transform(wc_Sha512* sha, const unsigned char* data)
         return BAD_FUNC_ARG;
     }
 
-#ifdef WOLFSSL_SMALL_STACK
-    buffer = (word64 *)XMALLOC(sizeof(word64) * 16, sha->heap,
-                               DYNAMIC_TYPE_TMP_BUFFER);
-    if (buffer == NULL)
-        return MEMORY_E;
-#endif
-
 #if defined(USE_INTEL_SPEEDUP) && \
     (defined(HAVE_INTEL_AVX1) || defined(HAVE_INTEL_AVX2))
     Sha512_SetTransform();
@@ -1271,6 +1270,15 @@ static int InitSha384(wc_Sha384* sha384)
         return BAD_FUNC_ARG;
     }
 
+#ifdef WOLFSSL_SMALL_STACK_CACHE
+    if (sha384->W == NULL) {
+        sha384->W = (word64 *)XMALLOC((sizeof(word64) * 16) + WC_SHA512_BLOCK_SIZE,
+                                      sha384->heap, DYNAMIC_TYPE_DIGEST);
+        if (sha384->W == NULL)
+            return MEMORY_E;
+    }
+#endif
+
     sha384->digest[0] = W64LIT(0xcbbb9d5dc1059ed8);
     sha384->digest[1] = W64LIT(0x629a292a367cd507);
     sha384->digest[2] = W64LIT(0x9159015a3070dd17);
@@ -1437,6 +1445,7 @@ void wc_Sha384Free(wc_Sha384* sha384)
 
 #ifdef WOLFSSL_SMALL_STACK_CACHE
     if (sha384->W != NULL) {
+        ForceZero(sha384->W, (sizeof(word64) * 16) + WC_SHA512_BLOCK_SIZE);
         XFREE(sha384->W, sha384->heap, DYNAMIC_TYPE_TMP_BUFFER);
         sha384->W = NULL;
     }
@@ -1507,7 +1516,12 @@ int wc_Sha512Copy(wc_Sha512* src, wc_Sha512* dst)
 
     XMEMCPY(dst, src, sizeof(wc_Sha512));
 #ifdef WOLFSSL_SMALL_STACK_CACHE
-    dst->W = NULL;
+    dst->W = (word64 *)XMALLOC((sizeof(word64) * 16) + WC_SHA512_BLOCK_SIZE,
+                               dst->heap, DYNAMIC_TYPE_DIGEST);
+    if (dst->W == NULL) {
+        XMEMSET(dst, 0, sizeof(wc_Sha512));
+        return MEMORY_E;
+    }
 #endif
 
 #ifdef WOLFSSL_SILABS_SHA512
@@ -1725,7 +1739,12 @@ int wc_Sha384Copy(wc_Sha384* src, wc_Sha384* dst)
 
     XMEMCPY(dst, src, sizeof(wc_Sha384));
 #ifdef WOLFSSL_SMALL_STACK_CACHE
-    dst->W = NULL;
+    dst->W = (word64 *)XMALLOC((sizeof(word64) * 16) + WC_SHA384_BLOCK_SIZE,
+                               dst->heap, DYNAMIC_TYPE_DIGEST);
+    if (dst->W == NULL) {
+        XMEMSET(dst, 0, sizeof(wc_Sha384));
+        return MEMORY_E;
+    }
 #endif
 
 #ifdef WOLFSSL_SILABS_SHA384