diff --git a/pkg/evaluators/authorization.go b/pkg/evaluators/authorization.go
index 75df06d3..a23f5059 100644
--- a/pkg/evaluators/authorization.go
+++ b/pkg/evaluators/authorization.go
@@ -57,7 +57,7 @@ func (config *AuthorizationConfig) Call(pipeline auth.AuthPipeline, ctx context.
 		var cacheKey interface{}
 
 		if cache != nil {
-			cacheKey = cache.ResolveKeyFor(pipeline.GetAuthorizationJSON())
+			cacheKey, _ = cache.ResolveKeyFor(pipeline.GetAuthorizationJSON())
 			if cachedObj, err := cache.Get(cacheKey); err != nil {
 				logger.V(1).Error(err, "failed to retrieve data from the cache")
 			} else if cachedObj != nil {
diff --git a/pkg/evaluators/authorization/authzed.go b/pkg/evaluators/authorization/authzed.go
index cb65acda..1759b17b 100644
--- a/pkg/evaluators/authorization/authzed.go
+++ b/pkg/evaluators/authorization/authzed.go
@@ -48,10 +48,22 @@ func (a *Authzed) Call(pipeline auth.AuthPipeline, ctx gocontext.Context) (inter
 
 	authJSON := pipeline.GetAuthorizationJSON()
 
+	resource, err := authzedObjectFor(a.Resource, a.ResourceKind, authJSON)
+	if err != nil {
+		return nil, err
+	}
+	object, err := authzedObjectFor(a.Subject, a.SubjectKind, authJSON)
+	if err != nil {
+		return nil, err
+	}
+	permission, err := a.Permission.ResolveFor(authJSON)
+	if err != nil {
+		return nil, err
+	}
 	resp, err := client.CheckPermission(ctx, &authzedpb.CheckPermissionRequest{
-		Resource:   authzedObjectFor(a.Resource, a.ResourceKind, authJSON),
-		Subject:    &authzedpb.SubjectReference{Object: authzedObjectFor(a.Subject, a.SubjectKind, authJSON)},
-		Permission: fmt.Sprintf("%s", a.Permission.ResolveFor(authJSON)),
+		Resource:   resource,
+		Subject:    &authzedpb.SubjectReference{Object: object},
+		Permission: fmt.Sprintf("%s", permission),
 	})
 	if err != nil {
 		return nil, err
@@ -74,9 +86,17 @@ func (a *Authzed) Call(pipeline auth.AuthPipeline, ctx gocontext.Context) (inter
 	return obj, nil
 }
 
-func authzedObjectFor(name, kind json.JSONValue, authJSON string) *authzedpb.ObjectReference {
-	return &authzedpb.ObjectReference{
-		ObjectId:   fmt.Sprintf("%s", name.ResolveFor(authJSON)),
-		ObjectType: fmt.Sprintf("%s", kind.ResolveFor(authJSON)),
+func authzedObjectFor(name, kind json.JSONValue, authJSON string) (*authzedpb.ObjectReference, error) {
+	objectId, err := name.ResolveFor(authJSON)
+	if err != nil {
+		return nil, err
 	}
+	objectType, err := kind.ResolveFor(authJSON)
+	if err != nil {
+		return nil, err
+	}
+	return &authzedpb.ObjectReference{
+		ObjectId:   fmt.Sprintf("%s", objectId),
+		ObjectType: fmt.Sprintf("%s", objectType),
+	}, nil
 }
diff --git a/pkg/evaluators/authorization/kubernetes_authz.go b/pkg/evaluators/authorization/kubernetes_authz.go
index e37fa80f..a382248b 100644
--- a/pkg/evaluators/authorization/kubernetes_authz.go
+++ b/pkg/evaluators/authorization/kubernetes_authz.go
@@ -63,26 +63,58 @@ func (k *KubernetesAuthz) Call(pipeline auth.AuthPipeline, ctx gocontext.Context
 	}
 
 	authJSON := pipeline.GetAuthorizationJSON()
-	jsonValueToStr := func(value json.JSONValue) string {
-		return fmt.Sprintf("%s", value.ResolveFor(authJSON))
+	jsonValueToStr := func(value json.JSONValue) (string, error) {
+		resolved, err := value.ResolveFor(authJSON)
+		if err != nil {
+			return "", err
+		}
+		return fmt.Sprintf("%s", resolved), nil
 	}
 
+	user, err := jsonValueToStr(k.User)
+	if err != nil {
+		return nil, err
+	}
 	subjectAccessReview := kubeAuthz.SubjectAccessReview{
 		Spec: kubeAuthz.SubjectAccessReviewSpec{
-			User: jsonValueToStr(k.User),
+			User: user,
 		},
 	}
 
 	if k.ResourceAttributes != nil {
 		resourceAttributes := k.ResourceAttributes
 
+		namespace, err := jsonValueToStr(resourceAttributes.Namespace)
+		if err != nil {
+			return nil, err
+		}
+		group, err := jsonValueToStr(resourceAttributes.Group)
+		if err != nil {
+			return nil, err
+		}
+		resource, err := jsonValueToStr(resourceAttributes.Resource)
+		if err != nil {
+			return nil, err
+		}
+		name, err := jsonValueToStr(resourceAttributes.Name)
+		if err != nil {
+			return nil, err
+		}
+		subresource, err := jsonValueToStr(resourceAttributes.SubResource)
+		if err != nil {
+			return nil, err
+		}
+		verb, err := jsonValueToStr(resourceAttributes.Verb)
+		if err != nil {
+			return nil, err
+		}
 		subjectAccessReview.Spec.ResourceAttributes = &kubeAuthz.ResourceAttributes{
-			Namespace:   jsonValueToStr(resourceAttributes.Namespace),
-			Group:       jsonValueToStr(resourceAttributes.Group),
-			Resource:    jsonValueToStr(resourceAttributes.Resource),
-			Name:        jsonValueToStr(resourceAttributes.Name),
-			Subresource: jsonValueToStr(resourceAttributes.SubResource),
-			Verb:        jsonValueToStr(resourceAttributes.Verb),
+			Namespace:   namespace,
+			Group:       group,
+			Resource:    resource,
+			Name:        name,
+			Subresource: subresource,
+			Verb:        verb,
 		}
 	} else {
 		request := pipeline.GetHttp()
diff --git a/pkg/evaluators/cache.go b/pkg/evaluators/cache.go
index 05aa4559..b5bd3a75 100644
--- a/pkg/evaluators/cache.go
+++ b/pkg/evaluators/cache.go
@@ -16,7 +16,7 @@ var EvaluatorCacheSize int // in megabytes
 type EvaluatorCache interface {
 	Get(key interface{}) (interface{}, error)
 	Set(key, value interface{}) error
-	ResolveKeyFor(authJSON string) interface{}
+	ResolveKeyFor(authJSON string) (interface{}, error)
 	Shutdown() error
 }
 
@@ -58,7 +58,7 @@ func (c *evaluatorCache) Set(key, value interface{}) error {
 	}
 }
 
-func (c *evaluatorCache) ResolveKeyFor(authJSON string) interface{} {
+func (c *evaluatorCache) ResolveKeyFor(authJSON string) (interface{}, error) {
 	return c.keyTemplate.ResolveFor(authJSON)
 }
 
diff --git a/pkg/evaluators/identity.go b/pkg/evaluators/identity.go
index 1c712f01..887b8a41 100644
--- a/pkg/evaluators/identity.go
+++ b/pkg/evaluators/identity.go
@@ -84,7 +84,7 @@ func (config *IdentityConfig) Call(pipeline auth.AuthPipeline, ctx context.Conte
 		var cacheKey interface{}
 
 		if cache != nil {
-			cacheKey = cache.ResolveKeyFor(pipeline.GetAuthorizationJSON())
+			cacheKey, _ = cache.ResolveKeyFor(pipeline.GetAuthorizationJSON())
 			if cachedObj, err := cache.Get(cacheKey); err != nil {
 				logger.V(1).Error(err, "failed to retrieve data from the cache")
 			} else if cachedObj != nil {
@@ -197,7 +197,11 @@ func (config *IdentityConfig) ResolveExtendedProperties(pipeline auth.AuthPipeli
 	authJSON := pipeline.GetAuthorizationJSON()
 
 	for _, extendedProperty := range config.ExtendedProperties {
-		extendedIdentityObject[extendedProperty.Name] = extendedProperty.ResolveFor(extendedIdentityObject, authJSON)
+		resolved, err := extendedProperty.ResolveFor(extendedIdentityObject, authJSON)
+		if err != nil {
+			return nil, err
+		}
+		extendedIdentityObject[extendedProperty.Name] = resolved
 	}
 
 	return extendedIdentityObject, nil
diff --git a/pkg/evaluators/identity/plain.go b/pkg/evaluators/identity/plain.go
index d30f0636..d996d774 100644
--- a/pkg/evaluators/identity/plain.go
+++ b/pkg/evaluators/identity/plain.go
@@ -18,8 +18,10 @@ type Plain struct {
 
 func (p *Plain) Call(pipeline auth.AuthPipeline, ctx context.Context) (interface{}, error) {
 	pattern := json.JSONValue{Pattern: p.Pattern}
-	if object := pattern.ResolveFor(pipeline.GetAuthorizationJSON()); object != nil {
+	if object, err := pattern.ResolveFor(pipeline.GetAuthorizationJSON()); object != nil {
 		return object, nil
+	} else if err != nil {
+		return nil, err
 	}
 	return nil, fmt.Errorf("could not retrieve identity object or null")
 }
diff --git a/pkg/evaluators/identity_extension.go b/pkg/evaluators/identity_extension.go
index b945e10e..f57e1ed9 100644
--- a/pkg/evaluators/identity_extension.go
+++ b/pkg/evaluators/identity_extension.go
@@ -17,9 +17,9 @@ type IdentityExtension struct {
 	Overwrite bool
 }
 
-func (i *IdentityExtension) ResolveFor(identityObject map[string]any, authJSON string) interface{} {
+func (i *IdentityExtension) ResolveFor(identityObject map[string]any, authJSON string) (interface{}, error) {
 	if value, exists := identityObject[i.Name]; exists && !i.Overwrite {
-		return value
+		return value, nil
 	}
 	return i.Value.ResolveFor(authJSON)
 }
diff --git a/pkg/evaluators/identity_extension_test.go b/pkg/evaluators/identity_extension_test.go
index edeb3e73..922c1765 100644
--- a/pkg/evaluators/identity_extension_test.go
+++ b/pkg/evaluators/identity_extension_test.go
@@ -84,7 +84,9 @@ func TestResolveIdentityExtension(t *testing.T) {
 	}
 
 	for _, tc := range testCases {
-		actual, _ := json.StringifyJSON(tc.input.ResolveFor(obj, authJSON))
+		resolved, err := tc.input.ResolveFor(obj, authJSON)
+		assert.NilError(t, err)
+		actual, _ := json.StringifyJSON(resolved)
 		assert.Equal(t, actual, tc.expected, fmt.Sprintf("%s failed: got '%s', want '%s'", tc.name, string(actual), string(tc.expected)))
 	}
 }
diff --git a/pkg/evaluators/metadata.go b/pkg/evaluators/metadata.go
index e32eb01e..f04d5695 100644
--- a/pkg/evaluators/metadata.go
+++ b/pkg/evaluators/metadata.go
@@ -53,7 +53,7 @@ func (config *MetadataConfig) Call(pipeline auth.AuthPipeline, ctx context.Conte
 		var cacheKey interface{}
 
 		if cache != nil {
-			cacheKey = cache.ResolveKeyFor(pipeline.GetAuthorizationJSON())
+			cacheKey, _ = cache.ResolveKeyFor(pipeline.GetAuthorizationJSON())
 			if cachedObj, err := cache.Get(cacheKey); err != nil {
 				logger.V(1).Error(err, "failed to retrieve data from the cache")
 			} else if cachedObj != nil {
diff --git a/pkg/evaluators/metadata/generic_http.go b/pkg/evaluators/metadata/generic_http.go
index f9a8417f..80adec26 100644
--- a/pkg/evaluators/metadata/generic_http.go
+++ b/pkg/evaluators/metadata/generic_http.go
@@ -127,7 +127,11 @@ func (h *GenericHttp) buildRequest(ctx gocontext.Context, endpoint, authJSON str
 	}
 
 	for _, header := range h.Headers {
-		req.Header.Set(header.Name, fmt.Sprintf("%s", header.Value.ResolveFor(authJSON)))
+		headerValue, err := header.Value.ResolveFor(authJSON)
+		if err != nil {
+			return nil, err
+		}
+		req.Header.Set(header.Name, fmt.Sprintf("%s", headerValue))
 	}
 
 	req.Header.Set("Content-Type", contentType)
@@ -152,16 +156,24 @@ func (h *GenericHttp) buildRequest(ctx gocontext.Context, endpoint, authJSON str
 
 func (h *GenericHttp) buildRequestBody(authData string) (io.Reader, error) {
 	if h.Body != nil {
-		if body, err := json.StringifyJSON(h.Body.ResolveFor(authData)); err != nil {
-			return nil, fmt.Errorf("failed to encode http request")
+		if resolved, err := h.Body.ResolveFor(authData); err != nil {
+			return nil, err
 		} else {
-			return bytes.NewBufferString(body), nil
+			if body, err := json.StringifyJSON(resolved); err != nil {
+				return nil, fmt.Errorf("failed to encode http request")
+			} else {
+				return bytes.NewBufferString(body), nil
+			}
 		}
 	}
 
 	data := make(map[string]interface{})
 	for _, param := range h.Parameters {
-		data[param.Name] = param.Value.ResolveFor(authData)
+		if resolved, err := param.Value.ResolveFor(authData); err != nil {
+			return nil, err
+		} else {
+			data[param.Name] = resolved
+		}
 	}
 
 	switch h.ContentType {
diff --git a/pkg/evaluators/response.go b/pkg/evaluators/response.go
index 6ee4b156..f116ad7e 100644
--- a/pkg/evaluators/response.go
+++ b/pkg/evaluators/response.go
@@ -82,7 +82,7 @@ func (config *ResponseConfig) Call(pipeline auth.AuthPipeline, ctx context.Conte
 		var cacheKey interface{}
 
 		if cache != nil {
-			cacheKey = cache.ResolveKeyFor(pipeline.GetAuthorizationJSON())
+			cacheKey, _ = cache.ResolveKeyFor(pipeline.GetAuthorizationJSON())
 			if cachedObj, err := cache.Get(cacheKey); err != nil {
 				logger.V(1).Error(err, "failed to retrieve data from the cache")
 			} else if cachedObj != nil {
diff --git a/pkg/evaluators/response/dynamic_json.go b/pkg/evaluators/response/dynamic_json.go
index 7ab9d2ae..8dc04e00 100644
--- a/pkg/evaluators/response/dynamic_json.go
+++ b/pkg/evaluators/response/dynamic_json.go
@@ -24,7 +24,11 @@ func (j *DynamicJSON) Call(pipeline auth.AuthPipeline, ctx context.Context) (int
 
 	for _, property := range j.Properties {
 		value := property.Value
-		obj[property.Name] = value.ResolveFor(authJSON)
+		if resolved, err := value.ResolveFor(authJSON); err != nil {
+			return nil, err
+		} else {
+			obj[property.Name] = resolved
+		}
 	}
 
 	return obj, nil
diff --git a/pkg/evaluators/response/plain.go b/pkg/evaluators/response/plain.go
index c84f5ded..6e1e61d6 100644
--- a/pkg/evaluators/response/plain.go
+++ b/pkg/evaluators/response/plain.go
@@ -13,5 +13,5 @@ type Plain struct {
 
 func (p *Plain) Call(pipeline auth.AuthPipeline, ctx context.Context) (interface{}, error) {
 	authJSON := pipeline.GetAuthorizationJSON()
-	return p.ResolveFor(authJSON), nil
+	return p.ResolveFor(authJSON)
 }
diff --git a/pkg/evaluators/response/wristband.go b/pkg/evaluators/response/wristband.go
index db811703..1851d960 100644
--- a/pkg/evaluators/response/wristband.go
+++ b/pkg/evaluators/response/wristband.go
@@ -120,7 +120,11 @@ func (w *Wristband) Call(pipeline auth.AuthPipeline, ctx context.Context) (inter
 
 		for _, claim := range w.CustomClaims {
 			value := claim.Value
-			claims[claim.Name] = value.ResolveFor(authJSON)
+			if resolved, err := value.ResolveFor(authJSON); err != nil {
+				return nil, err
+			} else {
+				claims[claim.Name] = resolved
+			}
 		}
 	}
 
diff --git a/pkg/expressions/cel/expressions.go b/pkg/expressions/cel/expressions.go
index 9d7be3f6..1663e83a 100644
--- a/pkg/expressions/cel/expressions.go
+++ b/pkg/expressions/cel/expressions.go
@@ -45,6 +45,29 @@ func (p *Predicate) Matches(json string) (bool, error) {
 	return result.Value().(bool), nil
 }
 
+type Expression struct {
+	program cel.Program
+	source  string
+}
+
+func (e *Expression) ResolveFor(json string) (interface{}, error) {
+	input, err := AuthJsonToCel(json)
+	if err != nil {
+		return nil, err
+	}
+
+	result, _, err := e.program.Eval(input)
+	if err != nil {
+		return nil, err
+	}
+
+	if jsonVal, err := ValueToJSON(result); err != nil {
+		return nil, err
+	} else {
+		return jsonVal, nil
+	}
+}
+
 func Compile(expression string, predicate bool, opts ...cel.EnvOption) (cel.Program, error) {
 	envOpts := append([]cel.EnvOption{cel.Declarations(
 		decls.NewConst(RootAuthBinding, decls.NewObjectType("google.protobuf.Struct"), nil),
diff --git a/pkg/expressions/types.go b/pkg/expressions/types.go
new file mode 100644
index 00000000..d0406fa9
--- /dev/null
+++ b/pkg/expressions/types.go
@@ -0,0 +1,5 @@
+package expressions
+
+type Value interface {
+	ResolveFor(jsonData string) (interface{}, error)
+}
diff --git a/pkg/json/json.go b/pkg/json/json.go
index b7eddcd4..4fe110d6 100644
--- a/pkg/json/json.go
+++ b/pkg/json/json.go
@@ -38,7 +38,11 @@ type JSONValue struct {
 // simple pattern or as a template that mixes static value with variable placeholders that resolve to patterns.
 // In case of a template that mixes no variable placeholder, but it contains nothing but a static string value, users
 // should use `JSONValue.Static` instead of `JSONValue.Pattern`.
-func (v *JSONValue) ResolveFor(jsonData string) interface{} {
+func (v *JSONValue) ResolveFor(jsonData string) (interface{}, error) {
+	return v.resolveForSafe(jsonData), nil
+}
+
+func (v *JSONValue) resolveForSafe(jsonData string) interface{} {
 	if v.Pattern != "" {
 		// If all curly braces in the pattern are for passing arguments to modifiers, then it's likely NOT a template.
 		// To be a template, the pattern must contain at least one curly brace delimiting a variable placeholder.
diff --git a/pkg/json/json_test.go b/pkg/json/json_test.go
index 0205e048..b5510115 100644
--- a/pkg/json/json_test.go
+++ b/pkg/json/json_test.go
@@ -33,17 +33,17 @@ func TestJSONValueResolveFor(t *testing.T) {
 	var resolvedValueAsJSON []byte
 
 	value = JSONValue{Static: "foo"}
-	assert.Equal(t, value.ResolveFor(jsonData), "foo")
-	assert.Equal(t, value.ResolveFor(""), "foo")
+	assert.Equal(t, value.resolveForSafe(jsonData), "foo")
+	assert.Equal(t, value.resolveForSafe(""), "foo")
 
 	value = JSONValue{Pattern: "auth.identity.username"}
-	assert.Equal(t, value.ResolveFor(jsonData), "john")
+	assert.Equal(t, value.resolveForSafe(jsonData), "john")
 
 	value = JSONValue{Pattern: "auth.identity.email_verified"}
-	assert.Equal(t, value.ResolveFor(jsonData), true)
+	assert.Equal(t, value.resolveForSafe(jsonData), true)
 
 	value = JSONValue{Pattern: "auth.identity.address"}
-	resolvedValueAsJSON, _ = json.Marshal(value.ResolveFor(jsonData))
+	resolvedValueAsJSON, _ = json.Marshal(value.resolveForSafe(jsonData))
 	type address struct {
 		Line1      string `json:"line_1"`
 		PostalCode int    `json:"postal_code"`
@@ -54,22 +54,22 @@ func TestJSONValueResolveFor(t *testing.T) {
 	assert.Equal(t, resolvedAddress.PostalCode, 987654)
 
 	value = JSONValue{Pattern: "auth.identity.roles"}
-	resolvedValueAsJSON, _ = json.Marshal(value.ResolveFor(jsonData))
+	resolvedValueAsJSON, _ = json.Marshal(value.resolveForSafe(jsonData))
 	var resolvedRoles []string
 	_ = json.Unmarshal(resolvedValueAsJSON, &resolvedRoles)
 	assert.DeepEqual(t, resolvedRoles, []string{"user", "admin"})
 
 	// pattern mixing static and variable placeholders ("template")
 	value = JSONValue{Pattern: "Hello, {auth.identity.username}!"}
-	assert.Equal(t, value.ResolveFor(jsonData), "Hello, john!")
+	assert.Equal(t, value.resolveForSafe(jsonData), "Hello, john!")
 
 	// template with inner patterns passing arguments to modifier
 	value = JSONValue{Pattern: `Email domain: {auth.identity.email.@extract:{"sep":"@","pos":1}}`}
-	assert.Equal(t, value.ResolveFor(jsonData), "Email domain: test")
+	assert.Equal(t, value.resolveForSafe(jsonData), "Email domain: test")
 
 	// simple pattern passing arguments to modifier (not a template)
 	value = JSONValue{Pattern: `auth.identity.email.@extract:{"sep":"@","pos":1}`}
-	assert.Equal(t, value.ResolveFor(jsonData), "test")
+	assert.Equal(t, value.resolveForSafe(jsonData), "test")
 }
 
 func TestIsTemplate(t *testing.T) {
diff --git a/pkg/service/auth_pipeline.go b/pkg/service/auth_pipeline.go
index 7e2478ab..22e112ab 100644
--- a/pkg/service/auth_pipeline.go
+++ b/pkg/service/auth_pipeline.go
@@ -587,17 +587,20 @@ func (pipeline *AuthPipeline) customizeDenyWith(authResult auth.AuthResult, deny
 		authJSON := pipeline.GetAuthorizationJSON()
 
 		if denyWith.Message != nil {
-			authResult.Message, _ = json.StringifyJSON(denyWith.Message.ResolveFor(authJSON))
+			resolved, _ := denyWith.Message.ResolveFor(authJSON)
+			authResult.Message, _ = json.StringifyJSON(resolved)
 		}
 
 		if denyWith.Body != nil {
-			authResult.Body, _ = json.StringifyJSON(denyWith.Body.ResolveFor(authJSON))
+			resolved, _ := denyWith.Body.ResolveFor(authJSON)
+			authResult.Body, _ = json.StringifyJSON(resolved)
 		}
 
 		if len(denyWith.Headers) > 0 {
 			headers := make([]map[string]string, 0)
 			for _, header := range denyWith.Headers {
-				value, _ := json.StringifyJSON(header.Value.ResolveFor(authJSON))
+				resolved, _ := header.Value.ResolveFor(authJSON)
+				value, _ := json.StringifyJSON(resolved)
 				headers = append(headers, map[string]string{header.Name: value})
 			}
 			authResult.Headers = headers