diff --git a/extensions/composer/waf/waf.go b/extensions/composer/waf/waf.go
index f22d1f31..5edae97e 100644
--- a/extensions/composer/waf/waf.go
+++ b/extensions/composer/waf/waf.go
@@ -7,6 +7,8 @@
 package waf
 
 import (
+	"fmt"
+	"io"
 	"net"
 	"strconv"
 	"strings"
@@ -26,11 +28,35 @@ const (
 	metadataKeyBlockPhase    = "block_phase"
 )
 
+// wafRegistry tracks all WAF instances created for a single Envoy config version
+// (main config + per-route overrides) so they can be closed together in OnDestroy
+// to release memoized regex patterns from Coraza's global cache.
+type wafRegistry struct {
+	wafs []coraza.WAF
+}
+
+func (r *wafRegistry) add(w coraza.WAF) {
+	if w != nil {
+		r.wafs = append(r.wafs, w)
+	}
+}
+
+func (r *wafRegistry) closeAll(l *logger.Logger) {
+	for _, w := range r.wafs {
+		if c, ok := w.(io.Closer); ok {
+			if err := c.Close(); err != nil {
+				l.Error(fmt.Sprintf("waf: error closing WAF instance: %v", err))
+			}
+		}
+	}
+}
+
 type wafPluginFactory struct {
 	shared.EmptyHttpFilterFactory
-	config  coraza.WAF
-	mode    waf.WAFMode
-	metrics *metrics
+	config   coraza.WAF
+	mode     waf.WAFMode
+	metrics  *metrics
+	registry *wafRegistry
 }
 
 type perRouteWafPluginConfig struct {
@@ -38,6 +64,14 @@ type perRouteWafPluginConfig struct {
 	mode   waf.WAFMode
 }
 
+// OnDestroy releases memoized regex caches held by all WAF instances (main + per-route)
+// created by this factory. Called by Envoy when the factory is destroyed (e.g. config update).
+func (f *wafPluginFactory) OnDestroy() {
+	l := logger.GetLogger()
+	l.Sugar().Infof("waf: closing %d WAF instances", len(f.registry.wafs))
+	f.registry.closeAll(l)
+}
+
 func (f *wafPluginFactory) Create(handle shared.HttpFilterHandle) shared.HttpFilter {
 	config := f.config
 	mode := f.mode
@@ -66,6 +100,9 @@ func (f *wafPluginFactory) Create(handle shared.HttpFilterHandle) shared.HttpFil
 
 type wafPluginConfigFactory struct {
 	shared.EmptyHttpFilterConfigFactory
+	// registry is shared between the config factory and the plugin factory it creates,
+	// so per-route WAFs added after the factory is created can still be closed on destroy.
+	registry *wafRegistry
 }
 
 func (f *wafPluginConfigFactory) Create(
@@ -88,10 +125,14 @@ func (f *wafPluginConfigFactory) Create(
 		handle.Log(shared.LogLevelInfo, "waf: empty filter config")
 	}
 
+	f.registry = &wafRegistry{}
+	f.registry.add(wafConfig)
+
 	return &wafPluginFactory{
-		config:  wafConfig,
-		mode:    mode,
-		metrics: newMetrics(handle),
+		config:   wafConfig,
+		mode:     mode,
+		metrics:  newMetrics(handle),
+		registry: f.registry,
 	}, nil
 }
 
@@ -100,6 +141,9 @@ func (f *wafPluginConfigFactory) CreatePerRoute(unparsedConfig []byte) (any, err
 	if err != nil {
 		return nil, err
 	}
+	if f.registry != nil {
+		f.registry.add(wafConfig)
+	}
 	return &perRouteWafPluginConfig{
 		config: wafConfig,
 		mode:   mode,
diff --git a/extensions/composer/waf/waf_test.go b/extensions/composer/waf/waf_test.go
index 0f1ebeb5..86a7339e 100644
--- a/extensions/composer/waf/waf_test.go
+++ b/extensions/composer/waf/waf_test.go
@@ -7,7 +7,10 @@ package waf
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
+	"runtime"
+	"runtime/debug"
 	"strconv"
 	"testing"
 
@@ -1901,3 +1904,74 @@ func Test_PerRouteConfigBlocksRequest(t *testing.T) {
 
 	wafPlugin.OnStreamComplete()
 }
+
+// Verifies that OnDestroy() keeps heap growth bounded across
+// config reloads by releasing Coraza's memoized regex patterns.
+func Test_OnDestroyReleasesMemory(t *testing.T) {
+	const (
+		reloads     = 30
+		rulesPerWAF = 50
+	)
+
+	ruleID := 1
+	makeDirectives := func() []string {
+		directives := []string{"SecRuleEngine On"}
+		for range rulesPerWAF {
+			directives = append(directives, fmt.Sprintf(
+				`SecRule REQUEST_URI "@rx ^/reload/%d/path$" "id:%d,phase:1,pass,nolog"`, ruleID, ruleID,
+			))
+			ruleID++
+		}
+		return directives
+	}
+
+	heapAlloc := func() uint64 {
+		// GC twice then scavenge: the first GC collects most objects, the second
+		// collects anything promoted or finalized during the first pass, and
+		// FreeOSMemory forces the runtime to return freed pages to the OS so that
+		// HeapAlloc reflects only genuinely live allocations.
+		runtime.GC()
+		runtime.GC()
+		debug.FreeOSMemory()
+		var m runtime.MemStats
+		runtime.ReadMemStats(&m)
+		return m.HeapAlloc
+	}
+
+	baseline := heapAlloc()
+
+	for range reloads {
+		// Use a fresh controller per reload so gomock state doesn't accumulate
+		// and skew the heap measurement.
+		ctrl := gomock.NewController(t)
+
+		mainConfig, err := json.Marshal(map[string]any{"directives": makeDirectives(), "mode": "FULL"})
+		require.NoError(t, err)
+		perRouteConfig, err := json.Marshal(map[string]any{"directives": makeDirectives(), "mode": "FULL"})
+		require.NoError(t, err)
+
+		configHandle := mocks.NewMockHttpFilterConfigHandle(ctrl)
+		configHandle.EXPECT().DefineCounter("waf_tx_total").Return(shared.MetricID(1), shared.MetricsSuccess)
+		configHandle.EXPECT().DefineCounter("waf_tx_blocked", "authority", "phase", "rule_id").Return(shared.MetricID(2), shared.MetricsSuccess)
+
+		configFactory := &wafPluginConfigFactory{}
+		factory, err := configFactory.Create(configHandle, mainConfig)
+		require.NoError(t, err)
+		_, err = configFactory.CreatePerRoute(perRouteConfig)
+		require.NoError(t, err)
+
+		// Simulate Envoy destroying the old factory when a config reload arrives.
+		factory.OnDestroy()
+		ctrl.Finish()
+	}
+
+	const maxGrowthKB = uint64(1024)
+	after := heapAlloc()
+	heapGrowthKB := (max(after, baseline) - baseline) / 1024
+
+	// Without OnDestroy releasing memoized caches: 30 reloads × 2 WAFs × 50 unique
+	// regexes leaks ~11+ MB. With Close(), heap growth stays under 1 MB.
+	assert.LessOrEqual(t, heapGrowthKB, maxGrowthKB,
+		"heap grew %d KB after %d reloads, expected ≤ %d KB: OnDestroy must call Close() on all WAF instances to release Coraza's memoized regex cache",
+		heapGrowthKB, reloads, maxGrowthKB)
+}