Missing XML Validation

The product accepts XML from an untrusted source but does not validate the XML against the proper schema.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

The product accepts XML from an untrusted source but does not validate the XML against the proper schema.

Extended description

Most successful attacks begin with a violation of the programmer's assumptions. By accepting an XML document without validating it against a DTD or XML schema, the programmer leaves a door open for attackers to provide unexpected, unreasonable, or malicious input.

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Risk

What does successful exploitation lead to?

Unexpected State

Affected security scopes: Integrity

Defence

How is it prevented and fixed?

Architecture and Design

Input Validation

Detail

Always validate XML input against a known XML Schema or DTD. It is not possible for an XML parser to validate all aspects of a document's content because a parser cannot understand the complete semantics of the data. However, a parser can do a complete and thorough job of checking the document's structure and therefore guarantee to the code that processes the document that the content is well-formed.

Verification

How is it detected?

Automated Static Analysis

High

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)