How severe is CVE-2026-40190?

CVE-2026-40190 has a CVSS 3.x base score of 5.6, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2026-40190 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (23rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40190?

CVE-2026-40190 affects Langchain Langsmith. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40190?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-40190 have an EU (EUVD) identifier?

Yes. CVE-2026-40190 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-21594.

When was CVE-2026-40190 published?

CVE-2026-40190 was published on 2026-04-10 and last updated on 2026-07-07.

CVE-2026-40190

CVE-2026-40190 is a medium-severity vulnerability in Langchain Langsmith with a CVSS 3.x base score of 5.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1321.

Key facts

Severity: Medium (CVSS 3.x base score 5.6)
EPSS exploit prediction: 0% (23rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-21594
Weakness: CWE-1321
Affected product: Langchain Langsmith
Published: 2026-04-10
Last modified: 2026-07-07

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.

Frequently asked questions

What is CVE-2026-40190?: 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.
How severe is CVE-2026-40190?: CVE-2026-40190 has a CVSS 3.x base score of 5.6, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2026-40190 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (23rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40190?: CVE-2026-40190 affects Langchain Langsmith. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40190?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40190 have an EU (EUVD) identifier?: Yes. CVE-2026-40190 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-21594.
When was CVE-2026-40190 published?: CVE-2026-40190 was published on 2026-04-10 and last updated on 2026-07-07.

References

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

Affected products (1)

cpe:2.3:a:langchain:langsmith:*:*:*:*:*:node.js:*:*

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