diff --git a/features/mbedtls/targets/TARGET_STM/sha256_alt.c b/features/mbedtls/targets/TARGET_STM/sha256_alt.c
index 08f81fb4d2..a3354e9968 100644
--- a/features/mbedtls/targets/TARGET_STM/sha256_alt.c
+++ b/features/mbedtls/targets/TARGET_STM/sha256_alt.c
@@ -27,26 +27,44 @@ static void mbedtls_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
 }
 
-static void st_sha256_restore_hw_context(mbedtls_sha256_context *ctx)
+static int st_sha256_restore_hw_context(mbedtls_sha256_context *ctx)
 {
     uint32_t i;
+    uint32_t tickstart;
     /* allow multi-instance of HASH use: save context for HASH HW module CR */
+    /* Check that there is no HASH activity on going */
+    tickstart = HAL_GetTick();
+    while ((HASH->SR & (HASH_FLAG_BUSY | HASH_FLAG_DMAS)) != 0) {
+        if ((HAL_GetTick() - tickstart) > ST_SHA256_TIMEOUT) {
+            return 0; // timeout: HASH processor is busy
+        }
+    }
     HASH->STR = ctx->ctx_save_str;
-    HASH->CR = (ctx->ctx_save_cr|HASH_CR_INIT);
+    HASH->CR = (ctx->ctx_save_cr | HASH_CR_INIT);
     for (i=0;i<38;i++) {
         HASH->CSR[i] = ctx->ctx_save_csr[i];
     }
+    return 1;
 }
 
-static void st_sha256_save_hw_context(mbedtls_sha256_context *ctx)
+static int st_sha256_save_hw_context(mbedtls_sha256_context *ctx)
 {
     uint32_t i;
+    uint32_t tickstart;
+    /* Check that there is no HASH activity on going */
+    tickstart = HAL_GetTick();
+    while ((HASH->SR & (HASH_FLAG_BUSY | HASH_FLAG_DMAS)) != 0) {
+        if ((HAL_GetTick() - tickstart) > ST_SHA256_TIMEOUT) {
+            return 0; // timeout: HASH processor is busy
+        }
+    }
     /* allow multi-instance of HASH use: restore context for HASH HW module CR */
     ctx->ctx_save_cr = HASH->CR;
     ctx->ctx_save_str = HASH->STR;
     for (i=0;i<38;i++) {
         ctx->ctx_save_csr[i] = HASH->CSR[i];
     }
+    return 1;
 }
 
 void mbedtls_sha256_init( mbedtls_sha256_context *ctx )
@@ -85,12 +103,16 @@ void mbedtls_sha256_starts( mbedtls_sha256_context *ctx, int is224 )
         // error found to be returned
         return;
     }
-    st_sha256_save_hw_context(ctx);
+    if (st_sha256_save_hw_context(ctx) != 1) {
+        return; // return HASH_BUSY timeout Error here
+    }
 }
 
 void mbedtls_sha256_process( mbedtls_sha256_context *ctx, const unsigned char data[ST_SHA256_BLOCK_SIZE] )
 {
-    st_sha256_restore_hw_context(ctx);
+    if (st_sha256_restore_hw_context(ctx) != 1) {
+        return; // Return HASH_BUSY timout error here
+    }
     if (ctx->is224 == 0) {
         if (HAL_HASHEx_SHA256_Accumulate(&ctx->hhash_sha256, (uint8_t *) data, ST_SHA256_BLOCK_SIZE) != 0) {
             return; // Return error code
@@ -101,16 +123,20 @@ void mbedtls_sha256_process( mbedtls_sha256_context *ctx, const unsigned char da
         }
     }
 
-    st_sha256_save_hw_context(ctx);
+    if (st_sha256_save_hw_context(ctx) != 1) {
+        return; // return HASH_BUSY timeout Error here
+    }
 }
 
 void mbedtls_sha256_update( mbedtls_sha256_context *ctx, const unsigned char *input, size_t ilen )
 {
     size_t currentlen = ilen;
-    st_sha256_restore_hw_context(ctx);
+    if (st_sha256_restore_hw_context(ctx) != 1) {
+        return; // Return HASH_BUSY timout error here
+    }
 
     // store mechanism to accumulate ST_SHA256_BLOCK_SIZE bytes (512 bits) in the HW
-    if (currentlen == 0){ // only change HW status is size if 0
+    if (currentlen == 0) { // only change HW status is size if 0
         if(ctx->hhash_sha256.Phase == HAL_HASH_PHASE_READY) {
             /* Select the SHA256 or SHA224 mode and reset the HASH processor core, so that the HASH will be ready to compute
              the message digest of a new message */
@@ -149,12 +175,16 @@ void mbedtls_sha256_update( mbedtls_sha256_context *ctx, const unsigned char *in
             memcpy(ctx->sbuf, input + ilen - ctx->sbuf_len, ctx->sbuf_len);
         }
     }
-    st_sha256_save_hw_context(ctx);
+    if (st_sha256_save_hw_context(ctx) != 1) {
+        return; // return HASH_BUSY timeout Error here
+    }
 }
 
 void mbedtls_sha256_finish( mbedtls_sha256_context *ctx, unsigned char output[32] )
 {
-    st_sha256_restore_hw_context(ctx);
+    if (st_sha256_restore_hw_context(ctx) != 1) {
+        return; // Return HASH_BUSY timout error here
+    }
     if (ctx->sbuf_len > 0) {
         if (ctx->is224 == 0) {
             if (HAL_HASHEx_SHA256_Accumulate(&ctx->hhash_sha256, ctx->sbuf, ctx->sbuf_len) != 0) {
@@ -179,7 +209,9 @@ void mbedtls_sha256_finish( mbedtls_sha256_context *ctx, unsigned char output[32
             return; // Return error code here
         }
     }
-    st_sha256_save_hw_context(ctx);
+    if (st_sha256_save_hw_context(ctx) != 1) {
+        return; // return HASH_BUSY timeout Error here
+    }
 }
 
 #endif /*MBEDTLS_SHA256_ALT*/
diff --git a/features/mbedtls/targets/TARGET_STM/sha256_alt.h b/features/mbedtls/targets/TARGET_STM/sha256_alt.h
index 04678706a2..b2ae7a3c29 100644
--- a/features/mbedtls/targets/TARGET_STM/sha256_alt.h
+++ b/features/mbedtls/targets/TARGET_STM/sha256_alt.h
@@ -31,7 +31,8 @@
 extern "C" {
 #endif
 
-#define ST_SHA256_BLOCK_SIZE ((size_t)(64)) // HW handles 512 bits, ie 64 bytes
+#define ST_SHA256_BLOCK_SIZE ((size_t)  64) // HW handles 512 bits, ie 64 bytes
+#define ST_SHA256_TIMEOUT    ((uint32_t) 3)
 /**
  * \brief          SHA-256 context structure
  * \note     HAL_HASH_SHA256_Accumulate will accumulate 512 bits packets, unless it is the last call to the  function