diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 93b4045..a3bc806 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3516,7 +3516,13 @@
     operation->md_alg = mbedtls_hash_info_md_from_psa(hash_alg);
     operation->alg = alg;
 
-    operation->hash = hash;
+    operation->hash = mbedtls_calloc(1, hash_length);
+
+    if (operation->hash == NULL) {
+        return PSA_ERROR_INSUFFICIENT_MEMORY;
+    }
+
+    memcpy(operation->hash, hash, hash_length);
     operation->hash_length = hash_length;
 
     return PSA_SUCCESS;
@@ -3643,8 +3649,12 @@
     if (operation->ctx) {
         mbedtls_ecdsa_free(operation->ctx);
         mbedtls_free(operation->ctx);
+        operation->ctx = NULL;
     }
 
+    mbedtls_free(operation->hash);
+    operation->hash = NULL;
+
     mbedtls_ecdsa_restart_free(&operation->restart_ctx);
 
     return PSA_SUCCESS;
@@ -3743,7 +3753,13 @@
 
     mbedtls_ecdsa_restart_init(&operation->restart_ctx);
 
-    operation->hash = hash;
+    operation->hash = mbedtls_calloc(1, hash_length);
+
+    if (operation->hash == NULL) {
+        return PSA_ERROR_INSUFFICIENT_MEMORY;
+    }
+
+    memcpy(operation->hash, hash, hash_length);
     operation->hash_length = hash_length;
 
     return PSA_SUCCESS;
@@ -3802,8 +3818,12 @@
     if (operation->ctx) {
         mbedtls_ecdsa_free(operation->ctx);
         mbedtls_free(operation->ctx);
+        operation->ctx = NULL;
     }
 
+    mbedtls_free(operation->hash);
+    operation->hash = NULL;
+
     mbedtls_ecdsa_restart_free(&operation->restart_ctx);
 
     mbedtls_mpi_free(&operation->r);
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index 610d780..f74db70 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -711,7 +711,8 @@
  * \retval #PSA_ERROR_NOT_SUPPORTED Either no internal interruptible operations
  *         are currently supported, or the key type is currently unsupported.
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
- *         There was insufficient memory to load the key representation.
+ *         There was insufficient memory either to load the key representation,
+ *         or to store the hash.
  */
 psa_status_t mbedtls_psa_sign_hash_start(
     mbedtls_psa_sign_hash_interruptible_operation_t *operation,
@@ -815,7 +816,8 @@
  *        Either no internal interruptible operations are currently supported,
  *         or the key type is currently unsupported.
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
- *        There was insufficient memory to load the key representation.
+ *        There was insufficient memory either to load the key representation,
+ *        or to store the hash.
  */
 psa_status_t mbedtls_psa_verify_hash_start(
     mbedtls_psa_verify_hash_interruptible_operation_t *operation,