XML attribute blowup is a denial of service attack against XML parsers. The attack provides a malicious XML document with many attributes in a single node. Vulnerable XML parsers process these attributes inefficiently, consuming excessive CPU and resulting in a denial of service through resource exhaustion. To prevent this, perimeter technologies should validate incoming XML and enforce limits on the number of attributes per element.

1. XML attribute blowup
Jitendra oza

2. XML
 XML stand for eXtensible Markup Language
 XML is mark up language like HTML
 XML was design to store and transport data
 XML tags are not predefined, you have to define you own tags
 XML design is self descriptive
 XML is W3C recommendation

3. XML structure
<?xml version=“1.0” encoding=“UTF-8” ?>
<note>
<To> Dikshant </To>
<From> Jeet </From>
<Message> Hey Buddy! </Message>
</note>

5. XML attribute
 XML elements can have attributes, just like HTML.
 Attributes are designed to contain data related to a specific element.
 Attributed must be quoted with ‘ ’ or “ ”
 Example:
 <person gender=“Male”>

6. XML Attribute Blowup
 XML Attribute Blowup is a denial of service attack against XML parsers
 The attacker provides a malicious XML documents, which vulnerable XML
parsers process in a very inefficient manner, leading to excessive CPU load.
 The essence of the attack is to include many attributes in the same XML node.
 Vulnerable XML parsers manage the attributes in an inefficient manner,
resulting in a non-linear overall run time, leading to a denial of service
condition via CPU exhaustion.

7. XML Attribute Blow Up
 Example:
<?xml version=“1.0”?>
<foo
A1=“”
A2=“”
..
..
A1000=“”
/>

8. Perimeter Solution
 Perimeter technologies should perform strict schema validation against all
incoming XML documents.
 The validation process should enforce the following configurable limits on XML
object definition :
 The maximum array size
 The maximum number of elements
 The maximum number of attributes per element
 The maximum size of entity definition
 The maximum number of references to entity definitions

9. Reference
 http://www.w3schools.com/xml/default.asp
 http://projects.webappsec.org/w/page/13247001/XML%20Attribute%20Blowu
p
 https://www.owasp.org/index.php/OWASP_Periodic_Table_of_Vulnerabilities
_-_SOAP_Array_Abuse,_XML_Attribute_Blowup,_XML_Entity_Expansion

10. Thank You