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CVE-2026-40190

LangSmith Client SDKs has Prototype Pollution in langsmith-sdk via Incomplete `__proto__` Guard in Internal lodash `set()`

Published: Apr 10, 2026Updated: May 29, 2026 Sources: CVE List NVDCWE-1321
5.6MEDIUM
NVD MITRE
EPSS Score
0.2%
Top 85.9%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:LI:LA:L
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:LConfidentiality
Low
I:LIntegrity
Low
A:LAvailability
Low
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Weaknesses

CWE-1321

Affected Products

langchain-ai
oss-projectaka langgraph, langchain, langchain-ai/langchain
langsmith-sdkMixed
AI / ML / ai-agent-tooling

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Execution
View detailed technique mapping

References

https://github.com/langchain-ai/langsmith-sdk/security/advisories/GHSA-fw9q-39r9-c252
github.com

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