CVE-2026-41690

Prototype pollution and path traversal in i18next-http-middleware via user-controlled language and namespace parameters

Published May 8, 2026 CVSS 3.1 · 8.6 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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

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

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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 8, 2026, 4:43 PM
Reserved
Apr 22, 2026, 3:53 AM
Status
Deferred
Published
May 8, 2026, 4:16 PM
Modified
Oct 26, 2026, 6:10 PM