diff --git a/ChangeLog.d/fix-null-pointer-dereference.txt b/ChangeLog.d/fix-null-pointer-dereference.txt
new file mode 100644
index 0000000000..1eb3c416a8
--- /dev/null
+++ b/ChangeLog.d/fix-null-pointer-dereference.txt
@@ -0,0 +1,4 @@
+Security
+   * Fix a NULL pointer dereference in mbedtls_x509_string_to_names() when
+     mbedtls_calloc() fails to allocate memory. This was caused by failing to
+     check whether mbedtls_calloc() returned NULL.
diff --git a/library/x509_create.c b/library/x509_create.c
index 370eb9b2e1..e424cbb47c 100644
--- a/library/x509_create.c
+++ b/library/x509_create.c
@@ -487,6 +487,9 @@ int mbedtls_x509_string_to_names(mbedtls_asn1_named_data **head, const char *nam
             } else {
                 oid.len = strlen(attr_descr->oid);
                 oid.p = mbedtls_calloc(1, oid.len);
+                if (oid.p == NULL) {
+                    return MBEDTLS_ERR_X509_ALLOC_FAILED;
+                }
                 memcpy(oid.p, attr_descr->oid, oid.len);
                 numericoid = 0;
             }