18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Versions prior to 3.9.3 allow an unauthenticated HTTP client to pollute Object.prototype in the Node.js process hosting the middleware, via two unvalidated entry points that reach internal object-key writes: getResourcesHandler and missingKeyHandler. This can break authorisation checks (if (user.isAdmin) returning true for any user), cause type-confusion DoS, and depending on downstream code it can be chained into RCE.

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-5fgg-jcpf-8jjw i18next-http-middleware: Prototype pollution and path traversal via user-controlled language and namespace parameters
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Sun, 10 May 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared I18next
I18next i18next-http-middleware
Vendors & Products I18next
I18next i18next-http-middleware

Fri, 08 May 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 08 May 2026 16:00:00 +0000

Type Values Removed Values Added
Description 18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Versions prior to 3.9.3 allow an unauthenticated HTTP client to pollute Object.prototype in the Node.js process hosting the middleware, via two unvalidated entry points that reach internal object-key writes: getResourcesHandler and missingKeyHandler. This can break authorisation checks (if (user.isAdmin) returning true for any user), cause type-confusion DoS, and depending on downstream code it can be chained into RCE.
Title Prototype pollution and path traversal in i18next-http-middleware via user-controlled language and namespace parameters
Weaknesses CWE-1321
CWE-22
References
Metrics cvssV3_1

{'score': 8.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-08T16:43:48.281Z

Reserved: 2026-04-22T03:53:24.407Z

Link: CVE-2026-41690

cve-icon Vulnrichment

Updated: 2026-05-08T16:42:42.875Z

cve-icon NVD

Status : Deferred

Published: 2026-05-08T16:16:11.473

Modified: 2026-05-12T15:29:40.830

Link: CVE-2026-41690

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-10T21:25:13Z

Weaknesses