XML Injection (aka Blind XPath Injection)

Opis

The product does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.

Within XML, special elements could include reserved words or characters such as "<", ">", """, and "&", which could then be used to add new data or modify XML syntax.

Skutki

• Confidentiality, Integrity, Availability

  Execute Unauthorized Code or Commands; Read Application Data; Modify Application Data

Zapobieganie

• Implementation · Input Validation

  Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

  When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

  Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Słabość nadrzędna

• CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

Słabości podrzędne

• CWE-643 Improper Neutralization of Data within XPath Expressions ('XPath Injection')
• CWE-652 Improper Neutralization of Data within XQuery Expressions ('XQuery Injection')

Kiedy powstaje

• Implementation — REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Dotyczy

Not Language-Specific

Uwagi

The description for this entry is generally applicable to XML, but the name includes "blind XPath injection" which is more closely associated with CWE-643. Therefore this entry might need to be deprecated or converted to a general category - although injection into raw XML is not covered by CWE-643 or CWE-652.

In vulnerability theory terms, this is a representation-specific case of a Data/Directive Boundary Error.

Under-reported. This is likely found regularly by third party code auditors, but there are very few publicly reported examples.

Źródła

1. Blind XPath Injection — Amit Klein, 2004
2. The Art of Software Security Assessment — Mark Dowd, John McDonald, Justin Schuh, Chapter 17, "XML Injection", Page 1069, Addison Wesley, 2006