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CVE-2026-40190

MEDIUM CVSS 3.1: 5.6 EPSS 0.05%
Updated Apr 10, 2026
LangSmith
Parameter Value
CVSS 5.6 (MEDIUM)
Fixed In 0.5.18
Type CWE-1321 (Prototype Pollution)
Vendor LangSmith
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
Low
Partial data leak
Integrity
Low
Partial data modification
Availability
Low
Partial disruption

CVSS Vector v3.1

Weakness Type (CWE)