CWE-611: Improper Restriction of XML External Entity Reference
Description
The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.
- Abstraction
- BaseA weakness specific enough to point to detection and prevention methods.
- Likelihood of exploit
- Not rated by MITRE
- Status
- Draft
Common consequences
- Confidentiality
Read Application Data; Read Files or Directories
If the attacker is able to include a crafted DTD and a default entity resolver is enabled, the attacker may be able to access arbitrary files on the system. By submitting an XML file that defines an external entity with a file:// URI, an attacker can cause the processing application to read the contents of a local...
- Integrity
Bypass Protection Mechanism
An attacker may supply a crafted DTD using URIs with schemes such as http://, forcing the application to make outgoing HTTP requests to servers that the attacker cannot reach directly, which can be used to bypass firewall restrictions; hide the source of attacks such as port scanning; or otherwise leverage the server's...
- Availability
DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
The product could consume excessive CPU cycles or memory using a URI that points to a large file, or a device that always returns data such as /dev/random. Alternately, the URI could reference a file that contains many nested or recursive entity references to further slow down parsing.
Potential mitigations
- ImplementationSystem Configuration
Many XML parsers and validators can be configured to disable external entity expansion.