CVE-2025-68665: LangChain serialization injection vulnerability enables secret extraction

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-23 · updated 2026-10-19
Weakness: CWE-502

Description

LangChain is a framework for building LLM-powered applications. Prior to @langchain/core versions 0.3.80 and 1.1.8, and prior to langchain versions 0.3.37 and 1.2.3, a serialization injection vulnerability exists in LangChain JS's toJSON() method (and subsequently when string-ifying objects using JSON.stringify(). The method did not escape objects with 'lc' keys when serializing free-form data in kwargs. The 'lc' key is used internally by LangChain to mark serialized objects. When user-controlled data contains this key structure, it is treated as a legitimate LangChain object during deserialization rather than plain user data. This issue has been patched in @langchain/core versions 0.3.80 and 1.1.8, and langchain versions 0.3.37 and 1.2.3

Affected products

@langchain Langchain.Js: before 0.3.37; from 1.0.0 before 1.2.3 — fixed in 0.3.37, 1.2.3
@langchain Langchain/Core: before 0.3.80; from 1.0.0 before 1.1.8 — fixed in 0.3.80, 1.1.8

How to fix

Upgrade to a fixed version: @langchain Langchain.Js 0.3.37, 1.2.3; @langchain Langchain/Core 0.3.80, 1.1.8. Check the vendor advisory for mitigations.

References

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