Looks like this issue was fixed in PHP 5.3 https://bugs.php.net/bug.php?id=39863| CARVIEW |
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date: Fri, 26 Dec 2025 12:23:38 GMT
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date: Fri, 26 Dec 2025 12:23:39 GMT
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PHP: Null bytes related issues - Manual
Null bytes related issues
As PHP uses the underlying C functions for filesystem related operations, it may handle null bytes in a quite unexpected way. As null bytes denote the end of a string in C, strings containing them won't be considered entirely but rather only until a null byte occurs. The following example shows a vulnerable code that demonstrates this problem:
Example #1 Script vulnerable to null bytes
<?php
$file = $_GET['file']; // "../../etc/passwd\0"
if (file_exists('/home/wwwrun/' . $file . '.php')) {
// File_exists will return true as the file /home/wwwrun/../../etc/passwd exists
include '/home/wwwrun/' . $file . '.php';
// The file /etc/passwd will be included
}
?>Therefore, any tainted string that is used in a filesystem operation should always be validated properly. Here is a better version of the previous example:
Example #2 Correctly validating the input
<?php
$file = $_GET['file'];
// Whitelisting possible values
switch ($file) {
case 'main':
case 'foo':
case 'bar':
include '/home/wwwrun/include/' . $file . '.php';
break;
default:
include '/home/wwwrun/include/main.php';
}
?>
＋add a note
User Contributed Notes 2 notes
Anonymous ¶
11 years ago
cornernote [at] gmail.com ¶
10 years ago
clean input of null bytes:
<?php
$clean = str_replace(chr(0), '', $input);
?>
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