diff --git a/src/DNS_Mgr.h b/src/DNS_Mgr.h
index 6b7049c5f3..b6d78311ce 100644
--- a/src/DNS_Mgr.h
+++ b/src/DNS_Mgr.h
@@ -207,17 +207,17 @@ public:
     bool Save();
 
     struct CachedStats {
-        unsigned long hosts;
-        unsigned long addresses;
-        unsigned long texts;
-        unsigned long total;
+        unsigned long hosts = 0;
+        unsigned long addresses = 0;
+        unsigned long texts = 0;
+        unsigned long total = 0;
     };
 
     struct Stats {
-        unsigned long requests; // These count only async requests.
-        unsigned long successful;
-        unsigned long failed;
-        unsigned long pending;
+        unsigned long requests = 0; // These count only async requests.
+        unsigned long successful = 0;
+        unsigned long failed = 0;
+        unsigned long pending = 0;
         CachedStats cached;
     };
 
diff --git a/src/PrefixTable.cc b/src/PrefixTable.cc
index 95fff9e09c..e83dd94326 100644
--- a/src/PrefixTable.cc
+++ b/src/PrefixTable.cc
@@ -138,7 +138,7 @@ void* PrefixTable::Remove(const Val* value) {
 }
 
 PrefixTable::iterator PrefixTable::InitIterator() {
-    iterator i;
+    iterator i = {};
     i.Xsp = i.Xstack;
     i.Xrn = tree->head;
     i.Xnode = nullptr;
diff --git a/src/PrefixTable.h b/src/PrefixTable.h
index 343ff8539f..fb2e2dd9c4 100644
--- a/src/PrefixTable.h
+++ b/src/PrefixTable.h
@@ -21,10 +21,10 @@ namespace detail {
 class PrefixTable {
 private:
     struct iterator {
-        patricia_node_t* Xstack[PATRICIA_MAXBITS + 1];
-        patricia_node_t** Xsp;
-        patricia_node_t* Xrn;
-        patricia_node_t* Xnode;
+        patricia_node_t* Xstack[PATRICIA_MAXBITS + 1] = {};
+        patricia_node_t** Xsp = nullptr;
+        patricia_node_t* Xrn = nullptr;
+        patricia_node_t* Xnode = nullptr;
     };
 
 public:
diff --git a/src/RuleAction.h b/src/RuleAction.h
index 5dbe688155..1d5c42d550 100644
--- a/src/RuleAction.h
+++ b/src/RuleAction.h
@@ -45,7 +45,7 @@ public:
 private:
     StringValPtr msg;
     EventHandlerPtr handler;
-    bool want_end_of_match; // Whether handler accepts end_of_match parameter.
+    bool want_end_of_match = false; // Whether handler accepts end_of_match parameter.
 };
 
 class RuleActionMIME : public RuleAction {
@@ -62,7 +62,7 @@ public:
 
 private:
     std::string mime;
-    int strength;
+    int strength = 0;
 };
 
 // Base class for enable/disable actions.
diff --git a/src/analyzer/protocol/mysql/mysql-protocol.pac b/src/analyzer/protocol/mysql/mysql-protocol.pac
index 60ea7e240c..f01a40f315 100644
--- a/src/analyzer/protocol/mysql/mysql-protocol.pac
+++ b/src/analyzer/protocol/mysql/mysql-protocol.pac
@@ -751,6 +751,7 @@ refine connection MySQL_Conn += {
 		deprecate_eof_ = false;
 		server_query_attrs_ = false;
 		client_query_attrs_ = false;
+		client_capabilities_ = 0;
 		query_attr_idx_ = 0;
 	%}
 
diff --git a/src/input/Manager.cc b/src/input/Manager.cc
index c8cc34ee1f..ad07695977 100644
--- a/src/input/Manager.cc
+++ b/src/input/Manager.cc
@@ -103,9 +103,9 @@ public:
     EventHandlerPtr event;
 
     RecordType* fields = nullptr;
-    unsigned int num_fields;
+    unsigned int num_fields = 0;
 
-    bool want_record;
+    bool want_record = false;
     EventStream();
     ~EventStream() override;
 };
diff --git a/src/script_opt/ZAM/IterInfo.h b/src/script_opt/ZAM/IterInfo.h
index 36b63c8c61..b42cc7e5a1 100644
--- a/src/script_opt/ZAM/IterInfo.h
+++ b/src/script_opt/ZAM/IterInfo.h
@@ -112,8 +112,8 @@ private:
     TableValPtr tv = nullptr;
 
     std::vector<ZVal*> loop_vars;
-    const std::vector<TypePtr>* loop_var_types;
-    const std::vector<bool>* lvt_is_managed;
+    const std::vector<TypePtr>* loop_var_types = nullptr;
+    const std::vector<bool>* lvt_is_managed = nullptr;
     TypePtr value_var_type;
 
     std::optional<DictIterator<TableEntryVal>> tbl_iter;
diff --git a/src/storage/backend/sqlite/SQLite.h b/src/storage/backend/sqlite/SQLite.h
index c10be5c905..927c501bac 100644
--- a/src/storage/backend/sqlite/SQLite.h
+++ b/src/storage/backend/sqlite/SQLite.h
@@ -74,8 +74,8 @@ private:
 
     std::string full_path;
     std::string table_name;
-    std::chrono::milliseconds pragma_timeout;
-    std::chrono::milliseconds pragma_wait_on_busy;
+    std::chrono::milliseconds pragma_timeout = {};
+    std::chrono::milliseconds pragma_wait_on_busy = {};
 
     telemetry::GaugePtr page_count_metric;
     telemetry::GaugePtr file_size_metric;