CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Description
The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.
Submission Date :
Aug. 25, 2020, midnight
Modification Date :
2023-06-29 00:00:00+00:00
Organization :
MITRE
Extended Description
By adding or modifying attributes of an object prototype, it is possible to create attributes that exist on every object, or replace critical attributes with malicious ones. This can be problematic if the product depends on existence or non-existence of certain attributes, or uses pre-defined attributes of object prototype (such as hasOwnProperty, toString or valueOf).
This weakness is usually exploited by using a special attribute of objects called proto, constructor or prototype. Such attributes give access to the object prototype. This weakness is often found in code that assigns object attributes based on user input, or merges or clones objects recursively.
Example - 1
This function sets object attributes based on a dot-separated path.
objectToModify[attr] = {};}
if (typeof objectToModify[attr] !== 'object') {objectToModify = objectToModify[attr];}
const pathArray = path.split(".");const attributeToSet = pathArray.pop();let objectToModify = object;for (const attr of pathArray) {objectToModify[attributeToSet] = value;return object;}function setValueByPath (object, path, value) {This function does not check if the attribute resolves to the object prototype. These codes can be used to add "isAdmin: true" to the object prototype.
setValueByPath({}, "__proto__.isAdmin", true)setValueByPath({}, "constructor.prototype.isAdmin", true)By using a denylist of dangerous attributes, this weakness can be eliminated.
// // Ignore attributes which resolve to object prototype//
continue;}
objectToModify[attr] = {};}
if (attr === "__proto__" || attr === "constructor" || attr === "prototype") {if (typeof objectToModify[attr] !== "object") {objectToModify = objectToModify[attr];}
const pathArray = path.split(".");const attributeToSet = pathArray.pop();let objectToModify = object;for (const attr of pathArray) {objectToModify[attributeToSet] = value;return object;}function setValueByPath (object, path, value) {Related Weaknesses
This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined to give an overview of the different insight to similar items that may exist at higher and lower levels of abstraction.
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