CVE-2026-48121

Description

## 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 attacker with control over configurable checkpoint identifiers could read checkpoint data outside their authorized thread boundary. Potentially exposed data includes: - Checkpoint state - Metadata - Pending writes This is a confidentiality issue with cross-tenant data disclosure risk. ## Exploit example An attacker-controlled request can inject MongoDB operators: ```ts graph = new StateGraph(...) .compile({ checkpointer: new MongoDBSaver() }); graph.invoke(..., { configurable: { "thread_id": { "$gt": "" }, "checkpoint_ns": { "$ne": null } } }); ``` If this payload is forwarded into `config.configurable`, the resulting query may match checkpoints outside the intended tenant/thread scope. ## Security hardening changes Version `1.3.1` hardens `@langchain/langgraph-checkpoint-mongodb` by adding runtime validation for configurable checkpoint identifiers and rejecting invalid values before MongoDB query/write paths execute. The patch also includes regression tests covering object/operator payloads across affected methods. ## Migration guide Upgrade to `@langchain/[email protected]` or later. No API migration is required for valid callers. However, applications that currently pass non-string identifier values in `config.configurable` will now receive explicit errors and should normalize/validate inputs. As defense in depth, validate identifier fields at API boundaries and avoid passing raw client objects into graph config. ## Resources - Issue: https://github.com/langchain-ai/langgraphjs/issues/2351 - Fix PR: https://github.com/langchain-ai/langgraphjs/pull/2397