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Date: February 2, 2021


Prototype pollution vulnerability in ‘dotty’ versions 0.0.1 through 0.1.0 allows attacker to cause a denial of service and may lead to remote code execution.


The NPM module `dotty` can be abused by Prototype Pollution vulnerability since the function `put()` does not check for the type of object before assigning value to the property. Due to this flaw an attacker could create a non-existent property or able to manipulate the property which leads to denial of service or potentially remote code execution.

PoC Details

The `put()` function accepts `object, path, value` arguments. Due to the absence of validation on the values passed into `path, value` an attacker can supply a malicious value by adjusting the `path` value to include the `__proto__` property. Since there is no validation before assigning the property to check whether the assigned argument is the Object's own property or not, the property `polluted` will be directly be assigned to the new object thereby polluting the Object prototype. Later in the code, if there is a check to validate `polluted` the valued would be substituted as "Yes! Its Polluted" as it had been polluted.

PoC Code

var dotty = require("dotty")
var obj = {}
console.log("Before : " + {}.polluted);
dotty.put(obj, '__proto__.polluted', 'Yes! Its Polluted');
console.log("After : " + {}.polluted);

Affected Environments



Upgrade to version 0.1.1

Language: JS

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Base Score:
Attack Vector (AV): Network
Attack Complexity (AC): Low
Privilegs Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): High
Integrity (I): High
Availability (A): High
Base Score:
Access Vector (AV): Network
Access Complexity (AC): Low
Authentication (AU): None
Confidentiality (C): Partial
Integrity (I): Partial
Availability (A): Partial
Additional information: