CAPEC-197 — Exponential Data Expansion
CAPEC-197: Exponential Data Expansion
MITRE CAPEC attack pattern
| Status | Draft |
| Typical severity | Medium |
| Likelihood of attack | High |
| Catalogue | CAPEC 3.9 (2023-01-24) |
Description
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.
Where this sits in the chain
A finding maps to a weakness (CWE), a weakness is exploited by an attack pattern (CAPEC), and an attack pattern shows up in ATT&CK as observed adversary behaviour. This page is the middle hop.
Weaknesses exploited: CWE-770, CWE-776
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.
Skills required
- Low: Ability to craft nested data expansion messages.
Consequences
- Availability: Unreliable Execution, Resource Consumption
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.