@langchain/langgraph-checkpoint-mongodb provides a LangGraph.js CheckpointSaver implementation that uses MongoDB for storage. Versions 1.3.0 and below are vulnerable to NoSQL injection: checkpoint identifiers (thread_id, checkpoint_ns, checkpoint_id) from config.configurable are passed into MongoDB find() queries in MongoDBSaver.getTuple() without type enforcement. If an attacker supplies an object payload (such as MongoDB operators $gt or $ne) instead of a string, it can be interpreted as a query operator, bypassing thread scoping and leaking checkpoints, including pending writes, across tenants. Applications are at risk if they forward untrusted input into config.configurable without coercing it to strings or validating it against a schema, particularly in multi-tenant or user-isolated setups. Apps that only use server-issued, string-typed identifiers with schema validation rejecting non-string fields are not affected. This issue has been fixed in version 1.3.1.

Affected: npm: @langchain/langgraph-checkpoint-mongodb

## Summary

A NoSQL injection vulnerability existed in `MongoDBSaver` where checkpoint identifier fields from `config.configurable` were used in MongoDB queries without strict type enforcement. In vulnerable versions, attacker-controlled object payloads (for example MongoDB operators like `$gt` and `$ne`) could be interpreted as query operators instead of literal identifier values.

This could bypass intended thread scoping and return checkpoints from other tenants.

## Attack surface

The vulnerable path was in `MongoDBSaver.getTuple()`, where `thread_id`, `checkpoint_ns`, and `checkpoint_id` were used in MongoDB `find()` queries. The same unvalidated values were then reused to fetch pending writes.

Applications were exposed when untrusted input was forwarded into `config.configurable` (for example, directly from request bodies or query parameters) without string coercion or schema validation.

## Who is affected?

Applications are vulnerable if they:

- Use `@langchain/langgraph-checkpoint-mongodb` with multi-tenant or user-isolated thread models. - Accept user-controlled values for `thread_id`, `checkpoint_ns`, or `checkpoint_id`. - Pass those values into `app.invoke()`, `app.stream()`, or direct saver methods without validation.

Applications are generally not vulnerable if they:

- Use server-issued identifiers only. - Source `thread_id` from trusted URL params that remain strings. - Enforce schema validation that rejects non-string identifier fields.

## Impact

An at…