langchain-ai langsmith-sdk up to 0.5.17 set prototype pollution

Summaryinfo

A vulnerability described as problematic has been identified in langchain-ai langsmith-sdk up to 0.5.17. Affected by this vulnerability is the function Set. The manipulation results in prototype pollution. This vulnerability was named CVE-2026-40190. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in langchain-ai langsmith-sdk up to 0.5.17. It has been classified as problematic. Affected is the function set. The manipulation with an unknown input leads to a prototype pollution vulnerability. CWE is classifying the issue as CWE-1321. The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-40190 since 04/09/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.

Upgrading to version 0.5.18 eliminates this vulnerability.

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Productinfo

Type

• Artificial Intelligence Software

Vendor

• langchain-ai

Name

• langsmith-sdk

Version

• 0.5.0
• 0.5.1
• 0.5.2
• 0.5.3
• 0.5.4
• 0.5.5
• 0.5.6
• 0.5.7
• 0.5.8
• 0.5.9
• 0.5.10
• 0.5.11
• 0.5.12
• 0.5.13
• 0.5.14
• 0.5.15
• 0.5.16
• 0.5.17

Website

• Product: https://github.com/langchain-ai/langsmith-sdk/

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