This library allows strings to be parsed as functions and stored as a specialized component, JsonFunctionValue. To do this, Javascripts eval function is used to execute strings that begin with function as Javascript. This unfortunately could allow arbitrary code to be executed if it exists as a value within the JSON structure being displayed. Given that this component may often be used to display data from arbitrary, untrusted sources, this is extremely dangerous. One important note is that users who have defined a custom onSubmitValueParser callback prop on the JsonTree component should be unaffected. This vulnerability exists in the default onSubmitValueParser prop which calls parse. Prop is added to JsonTree called allowFunctionEvaluation. This prop will be set to true in v2.2.2, which allows upgrade without losing backwards-compatibility. In v2.2.2, we switched from using eval to using Function to construct anonymous functions. This is better than eval for the following reasons: - Arbitrary code should not be able to execute immediately, since the Function constructor explicitly only creates anonymous functions - Functions are created without local closures, so they only have access to the global scope If you use: - Version <2.2.2, you must upgrade as soon as possible. - Version ^2.2.2, you must explicitly set JsonTrees allowFunctionEvaluation prop to false to fully mitigate this vulnerability. - Version >=3.0.0, allowFunctionEvaluation is already set to false by default, so no further steps are necessary.
Weakness
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before using the input in a dynamic evaluation call (e.g. “eval”).
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| React_editable_json_tree |
React_editable_json_tree_project |
* |
2.2.2 (excluding) |
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.
- Inputs should be decoded and canonicalized to the application’s current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control.
- Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.
- For Python programs, it is frequently encouraged to use the ast.literal_eval() function instead of eval, since it is intentionally designed to avoid executing code. However, an adversary could still cause excessive memory or stack consumption via deeply nested structures [REF-1372], so the python documentation discourages use of ast.literal_eval() on untrusted data [REF-1373].
References