Bug: PHP 5.3.7+ issue is_a function ( Ascii Version )

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PHP 5.3.7+ issue is_a function

Published
Credit
Risk
2011.11.11
Cipriano Groenendal
High
CWE
CVE
Local
Remote
CWE-94
CVE-2011-3379
No
Yes

CVSS Base Score
Impact Subscore
Exploitability Subscore
7.5/10
6.4/10
10/10
Exploit range
Attack complexity
Authentication
Remote
Low
No required
Confidentiality impact
Integrity impact
Availability impact
Partial
Partial
Partial

PHP 5.3.7 changed the behavior of the is_a() function, used to check if an object is an instance of a class, to call the
__autoload() function. This causes a remote code execute problem when coupled with a standard library like PEAR that
internally uses is_a to check if a returned variable is an Error object or not.

An unprotected __autoload() function that blindly includes based upon the variable it receives can be tricked into
including a remote file by, for example, uploading a specially crafted file containing a link to a remote website.

Full explanation + code example has been posted on our website at
http://www.byte.nl/blog/2011/09/23/security-bug-in-is_a-function-in-php-
5-3-7-5-3-8/ and has been e-mailed to security (at) php (dot) net [email concealed]

--
Cipriano Groenendal

References:

https://bugzilla.redhat.com/show_bug.cgi?id=741020
http://svn.php.net/viewvc/?view=revision&revision=317183
https://bugs.php.net/bug.php?id=55475
http://www.securityfocus.com/archive/1/519770/30/0/threaded
http://www.byte.nl/blog/2011/09/23/security-bug-in-is_a-function-in-php-5-3-7-5-3-8/

See this note in TXT Version

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Ascii Version