EUVD-2026-21594
GHSA-fw9q-39r9-c252
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
Lifecycle Timeline
4Description
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.
Analysis
Prototype pollution in LangSmith JavaScript/TypeScript SDK (langsmith) versions prior to 0.5.18 allows remote attackers to pollute Object.prototype via the createAnonymizer() API by supplying malicious constructor.prototype keys, bypassing an incomplete __proto__ filter. The vulnerability affects all objects in the Node.js process and can lead to information disclosure and integrity violations. …
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