CVE-2026-40190: medium-severity vulnerability in langchain-ai langsmith-sdk
LangSmith Client SDKs has Prototype Pollution in langsmith-sdk via Incomplete `__proto__` Guard in Internal lodash `set()`
Published · Updated
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.6epss 0.4%
exploitation probability
0.4%top 70% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
Affected products
langchain-ai · langsmith-sdkRelated CVEs — langchain-ai langsmith-sdk
In the same product, most dangerous first.
CVE-2026-25528MEDIUMLangSmith Client SDK Affected by Server-Side Request Forgery via Tracing Header InjectionEPSS 0.4%CVE-2026-41182MEDIUMLangSmith SDK: Streaming token events bypass output redactionEPSS 0.4%CVE-2026-45134HIGHLangSmith Client SDK: Public prompt pull deserializes untrusted manifests without trust boundary warningEPSS 0.3%CVE-2026-59152MEDIUMArbitrary server-side file read in LangSmith SDK TracingMiddlewareEPSS 0.2%