TI-2026-30207 Aliases CVE-2026-41690 GHSA-5fgg-jcpf-8jjw

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

MEDIUM 43CWE-1321Published 2026-05-08 · Updated 2026-05-08

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: —
Confidentiality · integrity · availability: Low · High · Low
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.0031 24th percentileScored 2026-11-07

Fix Fixed i18next-http-middleware (i18next): 3.9.3i18next-http-middleware (npm): 3.9.3

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
i18next	i18next-http-middleware	before 3.9.3	3.9.3	Patch available	CNA
—	i18next-http-middleware (npm)	before 3.9.3	3.9.3	Patch available	GHSA-5fgg-jcpf-8jjw

i18next-http-middleware Vendori18next Affected before 3.9.3 Fixed in 3.9.3 Patch available CNA
i18next-http-middleware (npm) Vendor— Affected before 3.9.3 Fixed in 3.9.3 Patch available GHSA-5fgg-jcpf-8jjw

Remediation

Fix · CNA i18next-http-middleware (i18next) Fixed in 3.9.3
Fix · GHSA-5fgg-jcpf-8jjw i18next-http-middleware (npm) Fixed in 3.9.3 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-41690
2026-10-03 Alias added: GHSA-5fgg-jcpf-8jjw

References

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-41690

Other 3

TI-2026-83444 Shared built-in object corruption in i18next resource merging CVSS 3.1MEDIUM 5.9
TI-2026-82145 Query parameter injection in i18next-http-backend via lng or ns CVSS 3.1LOW 3.7
TI-2026-68453 Incomplete URL validation in i18next-http-backend permits SSRF CVSS 3.1LOW 3.7
TI-2026-35995 i18next-http-middleware missingKeyHandler does not reject keys whose segments contain prototype-polluting names CVSS 3.1CRITICAL 9.1
TI-2026-35994 i18next-fs-backend: Prototype pollution via crafted missing-key string CVSS 3.1CRITICAL 9.1
TI-2026-79749 Protocol-relative URL injection in i18next-http-backend CVSS 4.0LOW 2.3

See all 13 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences