Vulnerability Intelligence Report
Prototype pollution and path traversal in i18next-http-middleware via user-controlled language and namespace parameters
CVE-2026-41690
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.
No Active Exploit Signals
CVSS Base Score
8.6
HIGH
Exploitability:3.9
Impact Score:4.8
EPSS Probability:0.31%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
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Authentication
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Weaponization
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SSVC Action
—
Weaknesses (CWE)
CWE-22 ↗CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-1321 ↗CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| i18next | i18next-http-middleware | < 3.9.3 (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
EPSS Score
0.310%
GitHub Advisory
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | GitHub, Inc. · Vendor · USA |
| Reserved | 2026-04-22T03:53:24 |
| Published | 2026-05-08T15:24:12 |
| Last Updated | 2026-05-08T16:43:48 |
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