| Name |
Data Serialization External Entities Blowup |
|
| Likelyhood of attack |
Typical severity |
| High |
Medium |
|
| Summary |
This attack takes advantage of the entity replacement property of certain data serialization languages (e.g., XML, YAML, etc.) where the value of the replacement is a URI. A well-crafted file could have the entity refer to a URI that consumes a large amount of resources to create a denial of service condition. This can cause the system to either freeze, crash, or execute arbitrary code depending on the URI. |
| Prerequisites |
A server that has an implementation that accepts entities containing URI values. |
| Solutions | This attack may be mitigated by tweaking the XML parser to not resolve external entities. If external entities are needed, then implement a custom XmlResolver that has a request timeout, data retrieval limit, and restrict resources it can retrieve locally. This attack may be mitigated by tweaking the serialized data parser to not resolve external entities. If external entities are needed, then implement a custom resolver that has a request timeout, data retrieval limit, and restrict resources it can retrieve locally. |
| Related Weaknesses |
|
CWE ID
|
Description
|
| CWE-611 |
Improper Restriction of XML External Entity Reference |
|
| Related CAPECS |
|
CAPEC ID
|
Description
|
| CAPEC-122 |
An adversary is able to exploit features of the target that should be reserved for privileged users or administrators but are exposed to use by lower or non-privileged accounts. Access to sensitive information and functionality must be controlled to ensure that only authorized users are able to access these resources. If access control mechanisms are absent or misconfigured, a user may be able to access resources that are intended only for higher level users. An adversary may be able to exploit this to utilize a less trusted account to gain information and perform activities reserved for more trusted accounts. This attack differs from privilege escalation and other privilege stealing attacks in that the adversary never actually escalates their privileges but instead is able to use a lesser degree of privilege to access resources that should be (but are not) reserved for higher privilege accounts. Likewise, the adversary does not exploit trust or subvert systems - all control functionality is working as configured but the configuration does not adequately protect sensitive resources at an appropriate level. |
| CAPEC-278 |
An adversary manipulates a web service related protocol to cause a web application or service to react differently than intended. This can either be performed through the manipulation of call parameters to include unexpected values, or by changing the called function to one that should normally be restricted or limited. By leveraging this pattern of attack, the adversary is able to gain access to data or resources normally restricted, or to cause the application or service to crash. |
|
| Taxonomy: WASC |
|
Entry ID
|
Entry Name
|
| 43 |
XML External Entities |
|