diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 521d1730..42bf356f 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -34,6 +34,20 @@ jobs:
         make clean
         make cppcheck
 
+  flawfinder:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - name: Create Build Environment
+      run: |
+        sudo apt-get update -qq
+        sudo apt-get install -qq flawfinder
+    - name: cppcheck
+      run: |
+        flawfinder --version
+        make clean
+        make flawfinder
+
   codespell:
     runs-on: ubuntu-latest
     steps:
diff --git a/Makefile b/Makefile
index 4d836e45..3844094f 100644
--- a/Makefile
+++ b/Makefile
@@ -222,10 +222,16 @@ lint:
 CPPCHECK_OPTIONS = --enable=warning,portability
 CPPCHECK_OPTIONS += --template=gcc
 CPPCHECK_OPTIONS += --suppress=selfAssignment
+CPPCHECK_OPTIONS += --suppress=integerOverflow
+CPPCHECK_OPTIONS += --error-exitcode=1
 .PHONY: cppcheck
 cppcheck:
 	cppcheck $(CPPCHECK_OPTIONS) --quiet --force ./src/
 
+.PHONY: flawfinder
+flawfinder:
+	flawfinder --minlevel 5 --error-level=5 ./src/
+
 IGNORE_WORDS = ba
 CODESPELL_OPTIONS = --write-changes --interactive 3 --enable-colors
 CODESPELL_OPTIONS += --ignore-words-list $(IGNORE_WORDS)
diff --git a/src/bacnet/basic/object/av.c b/src/bacnet/basic/object/av.c
index c4aa9b6d..39f11a62 100644
--- a/src/bacnet/basic/object/av.c
+++ b/src/bacnet/basic/object/av.c
@@ -946,8 +946,9 @@ void Analog_Value_Intrinsic_Reporting(uint32_t object_instance)
         ToState = CurrentAV->Ack_notify_data.EventState;
 
 #if PRINT_ENABLED
-        fprintf(stderr, "Send Acknotification for (%s,%d).\n",
-            bactext_object_type_name(OBJECT_ANALOG_VALUE), object_instance);
+        fprintf(stderr, "Send Acknotification for (%s,%u).\n",
+            bactext_object_type_name(OBJECT_ANALOG_VALUE),
+            (unsigned)object_instance);
 #endif /* PRINT_ENABLED */
 
         characterstring_init_ansi(&msgText, "AckNotification");
@@ -1094,8 +1095,9 @@ void Analog_Value_Intrinsic_Reporting(uint32_t object_instance)
             } /* switch (ToState) */
 
 #if PRINT_ENABLED
-            fprintf(stderr, "Event_State for (%s,%d) goes from %s to %s.\n",
-                bactext_object_type_name(OBJECT_ANALOG_VALUE), object_instance,
+            fprintf(stderr, "Event_State for (%s,%u) goes from %s to %s.\n",
+                bactext_object_type_name(OBJECT_ANALOG_VALUE),
+                (unsigned)object_instance,
                 bactext_event_state_name(FromState),
                 bactext_event_state_name(ToState));
 #endif /* PRINT_ENABLED */
diff --git a/src/bacnet/basic/object/bacfile.c b/src/bacnet/basic/object/bacfile.c
index 2689ee89..e34da9dc 100644
--- a/src/bacnet/basic/object/bacfile.c
+++ b/src/bacnet/basic/object/bacfile.c
@@ -544,7 +544,7 @@ bool bacfile_read_ack_stream_data(
     pFilename = bacfile_name(instance);
     if (pFilename) {
         found = true;
-        pFile = fopen(pFilename, "rb");
+        pFile = fopen(pFilename, "rb+");
         if (pFile) {
             (void)fseek(pFile, data->type.stream.fileStartPosition, SEEK_SET);
             if (fwrite(octetstring_value(&data->fileData[0]),
@@ -574,7 +574,7 @@ bool bacfile_read_ack_record_data(
     pFilename = bacfile_name(instance);
     if (pFilename) {
         found = true;
-        pFile = fopen(pFilename, "rb");
+        pFile = fopen(pFilename, "rb+");
         if (pFile) {
             if (data->type.record.fileStartRecord > 0) {
                 for (i = 0; i < (uint32_t)data->type.record.fileStartRecord;
diff --git a/src/bacnet/basic/service/h_arf.c b/src/bacnet/basic/service/h_arf.c
index a5fa6d26..1287ffbc 100644
--- a/src/bacnet/basic/service/h_arf.c
+++ b/src/bacnet/basic/service/h_arf.c
@@ -173,7 +173,7 @@ void handler_atomic_read_file(uint8_t *service_request,
 #if PRINT_ENABLED
                 fprintf(stderr, "ARF: fileStartRecord %d, %u RecordCount.\n",
                     (int)data.type.record.fileStartRecord,
-                    (int)data.type.record.RecordCount);
+                    (unsigned)data.type.record.RecordCount);
 #endif
                 len = arf_ack_encode_apdu(&Handler_Transmit_Buffer[pdu_len],
                     service_data->invoke_id, &data);
diff --git a/src/bacnet/basic/service/h_getevent.c b/src/bacnet/basic/service/h_getevent.c
index 5d682c74..1e0aadf8 100644
--- a/src/bacnet/basic/service/h_getevent.c
+++ b/src/bacnet/basic/service/h_getevent.c
@@ -55,7 +55,7 @@ void ge_ack_print_data(
     const char *state_strs[] = { "NO", "FA", "ON", "HL", "LL" };
     printf("DeviceID\tType\tInstance\teventState\n");
     printf("--------------- ------- --------------- ---------------\n");
-    int count = 0;
+    unsigned int count = 0;
     while (act_data) {
         printf("%u\t\t%u\t%u\t\t%s\n", device_id,
             act_data->objectIdentifier.type,
diff --git a/src/bacnet/property.c b/src/bacnet/property.c
index 60bff28c..a0bb0fbd 100644
--- a/src/bacnet/property.c
+++ b/src/bacnet/property.c
@@ -1509,7 +1509,7 @@ BACNET_PROPERTY_ID property_list_special_property(
 {
     int property = -1; /* return value */
     unsigned required, optional, proprietary;
-    struct special_property_list_t PropertyList = { { 0 } };
+    struct special_property_list_t PropertyList = { 0 };
 
     property_list_special(object_type, &PropertyList);
     required = PropertyList.Required.count;
@@ -1552,7 +1552,7 @@ unsigned property_list_special_count(
     BACNET_OBJECT_TYPE object_type, BACNET_PROPERTY_ID special_property)
 {
     unsigned count = 0; /* return value */
-    struct special_property_list_t PropertyList = { { 0 } };
+    struct special_property_list_t PropertyList = { 0 };
 
     property_list_special(object_type, &PropertyList);
     if (special_property == PROP_ALL) {