CAPEC-230 - XML Nested Payloads

Applications often need to transform data in and out of the XML format by using an XML parser. It may be possible for an attacker to inject data that may have an adverse effect on the XML parser when it is being processed. By nesting XML data and causing this data to be continuously self-referential, an attacker can cause the XML parser to consume more resources while processing, causing excessive memory consumption and CPU utilization. An attacker's goal is to leverage parser failure to his or her advantage. In most cases this type of an attack will result in a denial of service due to an application becoming unstable, freezing, or crash. However it may be possible to cause a crash resulting in arbitrary code execution, leading to a jump from the data plane to the control plane [R.230.1].

Severity

Likelihood

Confidentiality

Integrity

Availability

  • Attack Methods 2
  • Injection
  • API Abuse
  • Purposes 2
  • Penetration
  • Exploitation
  • Scopes 4
  • DoS: resource consumption (memory)
  • Availability
  • Read memory
  • Confidentiality
  • Execute unauthorized code or commands
  • Availability
  • Integrity
  • Confidentiality
  • Gain privileges / assume identity
  • Authorization
  • Access_Control
  • Confidentiality

Low level: Denial of service

High level: Arbitrary code execution

An application uses an XML parser to perform transformation on user-controllable data.

An application does not perform sufficient validation to ensure that user-controllable data is safe for an XML parser.

Step 1 -

An attacker determines the input data stream that is being processed by an XML parser on the victim's side..


Step 1 -

An attacker crafts input data that may have an adverse effect on the operation of the XML parser when the data is parsed on the victim's system..


Carefully validate and sanitize all user-controllable data prior to passing it to the XML parser routine. Ensure that the resultant data is safe to pass to the XML parser.

Perform validation on canonical data.

Pick a robust implementation of an XML parser.

Validate XML against a valid schema or DTD prior to parsing.