CVE-2026-55253: Langchain-Ai Langchain-MongoDB

High severity, CVSS 7.7. EPSS: 0.5% chance of exploitation in the next 30 days.

LangChain MongoDB provides integrations between MongoDB, Atlas, LangChain, and LangGraph. Prior to langgraph-checkpoint-mongodb 0.3.0 and langgraph-store-mongodb 0.4.0, MongoDBSaver.list(), MongoDBSaver.alist(), and MongoDBStore.search() incorporate filter dictionaries into MongoDB queries without recursively rejecting keys prefixed with $. An authenticated caller who controls a filter argument through HTTP query parameters, request body fields, or agent tool arguments can inject MongoDB Query Language operators such as $regex or $where. In a multi-tenant deployment that uses the filter to enforce per-user or per-tenant isolation, injected operators can bypass intended equality filtering and expose other tenants' checkpoint or store data. Filters constructed entirely from trusted server-side values have lower practical risk. This issue is fixed in langgraph-checkpoint-mongodb 0.3.0 and langgraph-store-mongodb 0.4.0.

Affected products

• Langchain-Ai Langchain-MongoDB: before 0.4.0 (fixed in 0.4.0)
• Langchain-Ai Langgraph-Checkpoint-MongoDB: before 0.3.0 (fixed in 0.3.0)
• Langchain-Ai Langgraph-Store-MongoDB: before 0.4.0 (fixed in 0.4.0)

Published 2026-09-14. Last modified 2026-09-30.