CVE-2026-40190

LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. Prior to 0.5.18, the LangSmith JavaScript/TypeScript SDK (langsmith) contains an incomplete prototype pollution fix in its internally vendored lodash set() utility. The baseAssignValue() function only guards against the __proto__ key, but fails to prevent traversal via constructor.prototype. This allows an attacker who controls keys in data processed by the createAnonymizer() API to pollute Object.prototype, affecting all objects in the Node.js process. This vulnerability is fixed in 0.5.18.

CVSS v3 5.6 MEDIUM

5.6^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 3.4

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact LOW

Scope UNCHANGED

References

Link	Resource
https://github.com/langchain-ai/langsmith-sdk/security/advisories/GHSA-fw9q-39r9-c252	Exploit Vendor Advisory Mitigation

Configurations

Configuration 1 (hide)

cpe:2.3:a:langchain:langsmith:*:*:*:*:*:node.js:*:*

History

07 Jul 2026, 18:33

Type	Values Removed	Values Added
References	~~() https://github.com/langchain-ai/langsmith-sdk/security/advisories/GHSA-fw9q-39r9-c252 -~~	() https://github.com/langchain-ai/langsmith-sdk/security/advisories/GHSA-fw9q-39r9-c252 - Exploit, Vendor Advisory, Mitigation
First Time		Langchain Langchain langsmith
CPE		cpe:2.3:a:langchain:langsmith::::::node.js::*

10 Apr 2026, 20:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-04-10 20:16

Updated : 2026-07-07 18:33

NVD link : CVE-2026-40190

Mitre link : CVE-2026-40190

CVE.ORG link : CVE-2026-40190

JSON object : View

Products Affected

langchain

langsmith

CWE

CWE-1321

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

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