XML external entity injection(XXE) is a vulnerability that allows an attacker to interfere with an applications processing of XML data. This attack occurs when XML input containing a reference to an external entity is processed by a weakly configured XML parser. The software 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. Here, XML external entity injection lead to External Service interaction & Internal file read in Business Central and also Kie-Server APIs.
Weakness
The product does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Process_automation_manager |
Redhat |
* |
7.13.1 (excluding) |
| RHPAM 7.13.1 async |
RedHat |
|
* |
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
References