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Insecure Library Loading
Highly critical

PHP "strip_tags()" Function and memory_limit Vulnerabilities

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Release Date:  2004-07-14    Views:  27,400

Secunia Advisory SA12064

Where:

From remote

Impact:

Security Bypass, System access

Solution Status:

Vendor Patch

CVE Reference(s):

Description


Stefan Esser has reported two vulnerabilities in PHP, which can be exploited by malicious people to bypass certain security functionality or compromise a vulnerable system.

1) The "strip_tags()" function fails to strip obfuscated HTML tags (e.g. tags with "\0"). This can be exploited to conduct cross-site scripting attacks against sites, which only rely on the "strip_tags()" functionality to prevent such attacks.

NOTE: An HTML tag such as "<script>" with an embedded binary character like "\0" is not a valid HTML entity. However, certain browsers such as Internet Explorer and Safari strip such illegal characters and render it. This is not a vulnerability in those browser, but unfortunate and unnecessary functionality.

2) Various errors within PHP's memory_limit request termination (e.g. when allocating Zend HashTables before proper initialisation) can be exploited to execute arbitrary code by corrupting the heap (e.g. supplying arbitrary HashTable destructor pointers).

Successful exploitation requires that a resource limit has been set via the "memory_limit" configuration directive.

The vulnerabilities have been reported in version 4.3.7 and prior and version 5.0.0RC3 and prior.


Solution:
The vulnerabilities have been fixed in version 4.3.8.

Further details available to Secunia VIM customers

Provided and/or discovered by:
Stefan Esser, e-matters.

Original Advisory:
Stefan Esser:
http://security.e-matters.de/advisories/112004.html
http://security.e-matters.de/advisories/122004.html

PHP:
http://www.php.net/release_4_3_8.php

Deep Links:
Links available to Secunia VIM customers

Do you have additional information related to this advisory?

Please provide information about patches, mitigating factors, new versions, exploits, faulty patches, links, and other relevant data by posting comments to this Advisory. You can also send this information to vuln@secunia.com

Subject: PHP "strip_tags()" Function and memory_limit Vulnerabilities

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