Fix GHSA-h96m-rvf9-jgm2

Author: ndossche

ext/standard/array.c

@@ -4272,7 +4272,7 @@ static zend_always_inline void php_array_merge_wrapper(INTERNAL_FUNCTION_PARAMET
 	uint32_t argc, i;
 	zval *src_entry;
 	HashTable *src, *dest;
-	uint32_t count = 0;
+	uint64_t count = 0;
 
 	ZEND_PARSE_PARAMETERS_START(0, -1)
 		Z_PARAM_VARIADIC('+', args, argc)
@@ -4292,6 +4292,11 @@ static zend_always_inline void php_array_merge_wrapper(INTERNAL_FUNCTION_PARAMET
 		count += zend_hash_num_elements(Z_ARRVAL_P(arg));
 	}
 
+	if (UNEXPECTED(count >= HT_MAX_SIZE)) {
+		zend_throw_error(NULL, "The total number of elements must be lower than %u", HT_MAX_SIZE);
+		RETURN_THROWS();
+	}
+
 	if (argc == 2) {
 		zval *ret = NULL;
 

ext/standard/tests/array/GHSA-h96m-rvf9-jgm2.phpt

@@ -0,0 +1,16 @@
+--TEST--
+GHSA-h96m-rvf9-jgm2
+--FILE--
+<?php
+
+$power = 20; // Chosen to be well within a memory_limit
+$arr = range(0, 2**$power);
+try {
+    array_merge(...array_fill(0, 2**(32-$power), $arr));
+} catch (Error $e) {
+    echo $e->getMessage(), "\n";
+}
+
+?>
+--EXPECTF--
+The total number of elements must be lower than %d