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The security advisory CVE-2026-106119 details a critical logic flaw in the LangChain.js MongoDB integration package.
The vulnerability specifically targets the MongoDBChatMessageHistory class responsible for managing conversational state.
At the root of the issue is the complete absence of runtime type enforcement for session identifiers.
Developers typically document that session identifiers must be passed strictly as standard string values.
However, TypeScript type annotations are entirely stripped out during the compilation to standard JavaScript.
Consequently, runtime JavaScript environments do not natively block non-string objects from entering methods.
Many web applications accept untrusted request parameters directly from user-controlled HTTP bodies or query strings.
When these raw inputs are passed into the MongoDBChatMessageHistory constructor, they bypass type expectations.
Affected applications typically store multiple distinct users’ conversation histories within the exact same MongoDB collection.
The separation between user sessions is maintained purely by filtering documents against the provided session identifier string.
MongoDB query engines interpret JavaScript objects containing special operator keys as active database query conditions.
An attacker can substitute a simple string identifier with a malicious structured object containing query operators.
For instance, injecting operators like conditions or regular expressions alters the underlying database filter logic.
Instead of matching a literal session string, MongoDB evaluates the injected operators against stored documents.
This manipulation successfully subverts the intended security isolation separating individual user conversation histories.
An authenticated or unauthenticated attacker capable of invoking chat operations can exploit this mechanism.
Once the query filter is hijacked, the adversary can read sensitive conversation logs belonging to other users.
Furthermore, the vulnerability permits malicious actors to modify or delete stored conversation records across sessions.
Applications that derive session identifiers securely from server-side authenticated sessions remain completely unaffected.
Similarly, applications utilizing isolated database collections per user do not experience cross-session data leakage.
The vulnerability carries a moderate CVSS score due to the requirement of interacting with chat endpoints.
Despite requiring specific application architectural patterns, the widespread use of shared collections increases exposure.
Security researchers identified this query condition injection vector during routine code audits of provider libraries.
The maintainers responded by releasing version 1.3.1 to incorporate robust runtime validation checks.
Upgrading to the patched release ensures that all session identifiers undergo strict type verification.
Additionally, the patched version explicitly wraps query parameters with literal comparison operators like $eq.
This dual-layer defense neutralizes both object injection attempts and unexpected type casting behaviors.
Developers unable to upgrade immediately must manually implement input validation to reject non-string session IDs.
Ensuring robust parameter sanitization prevents untrusted input from ever reaching database query construction layers.
This vulnerability serves as a reminder of the risks associated with trusting runtime types in database integrations.
DailyCVE Form:
Platform: @langchain/mongodb
Version: Older than 1.3.1
Vulnerability: NoSQL Query Injection
Severity: Medium
date: October 6 2026
Prediction: September 27 2026
What Undercode Say:
Bash Commands And Code
npm install @langchain/[email protected]
import { MongoDBChatMessageHistory } from "@langchain/mongodb";
const history = new MongoDBChatMessageHistory({
collection,
sessionId: verifiedSessionId,
});
Exploit: (Educational Purposes!)
const maliciousSessionId = { $ne: null };
const history = new MongoDBChatMessageHistory({
collection,
sessionId: maliciousSessionId,
});
Protection: from this CVE
Upgrade @langchain/mongodb to version 1.3.1 or later to enforce runtime string validation and literal query comparison wrapping.
Ensure session identifiers are strictly derived from authenticated server-controlled values rather than untrusted request payloads.
Reject any session input that fails to satisfy non-string or empty criteria before invoking chat history operations.
Impact:
Allows attackers to bypass session isolation and read, modify, or delete other users’ stored conversation histories within shared MongoDB collections.
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Sources:
Reported By: github.com
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