CAPEC Definitions / CAPEC-197
CAPEC-197: Exponential Data Expansion
An adversary submits data to a target application which contains nested exponential data expansion to produce excessively large output. Many data format languages allow the definition of macro-like structures that can be used to simplify the creation of complex structures. However, this capability can be abused to create excessive demands on a processor's CPU and memory. A small number of nested expansions can result in an exponential growth in demands on memory.
Extended Description
No Extended Description.
Mitigations
Design: Use libraries and templates that minimize unfiltered input. Use methods that limit entity expansion and throw exceptions on attempted entity expansion.
Implementation: For XML based data - disable altogether the use of inline DTD schemas when parsing XML objects. If a DTD must be used, normalize, filter and use an allowlist and parse with methods and routines that will detect entity expansion from untrusted sources.
Relationships with other CAPECs
CAPEC-230: Serialized Data with Nested Payloads
Prerequisites
This type of attack requires that the target must receive input but either fail to provide an upper limit for entity expansion or provide a limit that is so large that it does not preclude significant resource consumption.
