diff --git a/NEWS b/NEWS
index 15c85841eea..88cd54f5479 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,10 @@ PHP                                                                        NEWS
 - Filter:
   . Fix explicit FILTER_REQUIRE_SCALAR with FILTER_CALLBACK (ilutov)
 
+- Hash:
+  . Fixed bug GH-12186 (segfault copying/cloning a finalized HashContext).
+    (MaxSem)
+
 - SimpleXML:
   . Fixed bug GH-12170 (Can't use xpath with comments in SimpleXML). (nielsdos)
 
diff --git a/ext/hash/hash.c b/ext/hash/hash.c
index 2d29ff61fa0..c01a1f0f3ec 100644
--- a/ext/hash/hash.c
+++ b/ext/hash/hash.c
@@ -680,7 +680,7 @@ PHP_FUNCTION(hash_init)
 
 #define PHP_HASHCONTEXT_VERIFY(hash) { \
 	if (!hash->context) { \
-		zend_argument_type_error(1, "must be a valid Hash Context resource"); \
+		zend_argument_type_error(1, "must be a valid, non-finalized HashContext"); \
 		RETURN_THROWS(); \
 	} \
 }
@@ -837,11 +837,15 @@ PHP_FUNCTION(hash_final)
 PHP_FUNCTION(hash_copy)
 {
 	zval *zhash;
+	php_hashcontext_object *context;
 
 	if (zend_parse_parameters(ZEND_NUM_ARGS(), "O", &zhash, php_hashcontext_ce) == FAILURE) {
 		RETURN_THROWS();
 	}
 
+	context = php_hashcontext_from_object(Z_OBJ_P(zhash));
+	PHP_HASHCONTEXT_VERIFY(context);
+
 	RETVAL_OBJ(Z_OBJ_HANDLER_P(zhash, clone_obj)(Z_OBJ_P(zhash)));
 
 	if (php_hashcontext_from_object(Z_OBJ_P(return_value))->context == NULL) {
@@ -1405,6 +1409,11 @@ static zend_object *php_hashcontext_clone(zend_object *zobj) {
 	zend_object *znew = php_hashcontext_create(zobj->ce);
 	php_hashcontext_object *newobj = php_hashcontext_from_object(znew);
 
+	if (!oldobj->context) {
+		zend_throw_exception(zend_ce_value_error, "Cannot clone a finalized HashContext", 0);
+		return znew;
+	}
+
 	zend_objects_clone_members(znew, zobj);
 
 	newobj->ops = oldobj->ops;
diff --git a/ext/hash/tests/gh12186_1.phpt b/ext/hash/tests/gh12186_1.phpt
new file mode 100644
index 00000000000..5e34b1dd78e
--- /dev/null
+++ b/ext/hash/tests/gh12186_1.phpt
@@ -0,0 +1,17 @@
+--TEST--
+Hash: bug #12186 - segfault in hash_copy() on a finalized context
+--FILE--
+<?php
+
+$c = hash_init('sha1');
+hash_final($c);
+
+try {
+    hash_copy($c);
+} catch (Throwable $ex) {
+    echo $ex->getMessage() . "\n";
+}
+
+?>
+--EXPECTF--
+hash_copy(): Argument #1 ($context) must be a valid, non-finalized HashContext
diff --git a/ext/hash/tests/gh12186_2.phpt b/ext/hash/tests/gh12186_2.phpt
new file mode 100644
index 00000000000..64a12b15c39
--- /dev/null
+++ b/ext/hash/tests/gh12186_2.phpt
@@ -0,0 +1,17 @@
+--TEST--
+Hash: bug #12186 - segfault when cloning a finalized context
+--FILE--
+<?php
+
+$c = hash_init('sha1');
+hash_final($c);
+
+try {
+    clone $c;
+} catch (Throwable $ex) {
+    echo $ex->getMessage() . "\n";
+}
+
+?>
+--EXPECTF--
+Cannot clone a finalized HashContext
diff --git a/ext/hash/tests/reuse.phpt b/ext/hash/tests/reuse.phpt
index 229236dd713..b5cfc79c162 100644
--- a/ext/hash/tests/reuse.phpt
+++ b/ext/hash/tests/reuse.phpt
@@ -14,4 +14,4 @@ catch (\Error $e) {
 
 ?>
 --EXPECT--
-hash_update(): Argument #1 ($context) must be a valid Hash Context resource
+hash_update(): Argument #1 ($context) must be a valid, non-finalized HashContext