Bug 1297720

Summary: php: Use-after-free in WDDX Packet Deserialization
Product: [Other] Security Response Reporter: Adam Mariš <amaris>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED WONTFIX QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: abhgupta, carnil, cbuissar, dmcphers, fedora, jialiu, jokerman, jorton, kseifried, lmeyer, mmaslano, mmccomas, rcollet, tiwillia, webstack-team
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: php 5.5.31, php 5.6.17 Doc Type: Bug Fix
Doc Text:
A use-after-free flaw was found in the php_wddx_pop_element() function of PHP's WDDX extension. Unserializing specially crafted input could cause a PHP application to crash or, possibly, execute arbitrary code.
 Story Points: ---
Clone Of: Environment:
Last Closed: 2016-02-03 13:02:52 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1297722    
Bug Blocks: 1297732    

Description Adam Mariš 2016-01-12 10:17:14 UTC 
A use-after free vulnerability was found that could possible lead to arbitrary remote codeexecution. Vulnerable code:

if (Z_TYPE_P(ent2->data) == IS_ARRAY || Z_TYPE_P(ent2->data) == IS_OBJECT) {
	target_hash = HASH_OF(ent2->data);
	if (ent1->varname) {
		if (!strcmp(ent1->varname, PHP_CLASS_NAME_VAR) &&
			Z_TYPE_P(ent1->data) == IS_STRING && Z_STRLEN_P(ent1->data)) {
			...
			/* Clean up old array entry */
			zval_ptr_dtor(&ent2->data);
				
			/* Set stack entry to point to the newly created object */
			ent2->data = obj;
					
			/* Clean up class name var entry */
			zval_ptr_dtor(&ent1->data);

During wddx packet deserialization the zval_ptr_dtor() lead ZVAL is freed from the memory, however a crafted recordset can still use already freed memory.

Upstream patch:

https://git.php.net/?p=php-src.git;a=commit;h=366f9505a4aae98ef2f4ca39a838f628a324b746

Upstream bug (contains reproducer):

https://bugs.php.net/bug.php?id=70661
Comment 1 Adam Mariš 2016-01-12 10:18:09 UTC 
Created php tracking bugs for this issue:

Affects: fedora-all [bug 1297722]
Comment 2 Fedora Update System 2016-01-16 13:22:24 UTC 
php-5.6.17-1.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
Comment 3 Fedora Update System 2016-01-16 14:20:19 UTC 
php-5.6.17-1.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
Comment 4 Cedric Buissart 2016-01-29 10:36:30 UTC 
Lowering the impact down to moderate based on the following :
 * WDDX packet deserialization should not be used with untrusted source :
http://php.net/manual/en/function.wddx-deserialize.php#refsect1-function.wddx-deserialize-returnvalues