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Medium severity5.6NVD Advisory· Published Apr 10, 2026· Updated Jul 7, 2026

CVE-2026-40190

CVE-2026-40190

Description

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.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
langsmithnpm
< 0.5.180.5.18

Affected products

25

Patches

Vulnerability mechanics

References

5

News mentions

0

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