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Apache Flex BlazeDS 4.7.0 XML Entity Expansion

Posted on 24 August 2015
Source : packetstormsecurity.org Link

 

CVE-2015-3269 Apache Flex BlazeDS Insecure Xml Entity Expansion
Vulnerability

Severity: Important

Vendor: The Apache Software Foundation

Versions Affected: Apache Flex BlazeDS 4.7.0

Description: When receiving XML encoded AMF messages containing DTD
entities, the
default XML parser configurations allows expanding of entities to local
resources.
A request that included a specially crafted request parameter could be
used to
access content that would otherwise be protected.

Mitigation: All users of Apache Flex BlazeDS prior to 4.7.1

Example: For an AMF message that contains the following xml payload:
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE foo [
<!ELEMENT foo ANY >
<!ENTITY xxe SYSTEM "file:///etc/passwd" >]><foo>&xxe;</foo>
the entity &xxe; would be expanded to the content of the file /etc/passwd.
However this expanded information is not automatically transferred back to
the client, but could be made available by the application.

Credit: This issue was discovered by Matthias Kaiser of Code White

References:
https://www.owasp.org/index.php/XML_External_Entity_(XXE)_Processing

Christofer Dutz

 

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