CVE-2026-48714: i18next-http-middleware Prototype Pollution in missingKeyHandler

CVE-2026-48714 · Severity: critical · CVSS 9.1 · Published 2026-06-15

i18next-http-middleware is a tool used to handle translations in web applications. A security flaw allows attackers to send specially crafted requests that can modify the application's internal configuration or cause it to crash. This could lead to service outages, corrupted website content, or the bypass of certain security checks.

Technologies: i18next-http-middleware (npm). Vendors: npm.

Quick answers

Is CVE-2026-48714 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-48714 being exploited in the wild.
How severe is CVE-2026-48714?
Critical severity, with a CVSS score of 9.1, published 15 June 2026.
Which products and versions are affected?
i18next-http-middleware (npm) < 3.9.7, SEMVER:introduced=0,fixed=3.9.7.
Is there a fix for CVE-2026-48714?
Yes. i18next-http-middleware (npm): upgrade to 3.9.7 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-48714 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-48714?
Check whether you run i18next-http-middleware (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • i18next-http-middleware (npm): upgrade to 3.9.7 or later
    npm install i18next-http-middleware@3.9.7

Technical details

The missingKeyHandler in i18next-http-middleware (<= 3.9.6) fails to properly sanitize dotted key segments. While it blocks literal keys like '__proto__', it does not account for nested paths when a keySeparator (default '.') is used. When paired with a downstream backend like i18next-fs-backend (<= 2.6.5), these keys are passed to an unguarded setPath() function, leading to prototype pollution. An unauthenticated remote attacker can exploit this to inject properties into Object.prototype, potentially leading to RCE, DoS, or authorization bypass depending on the application environment. The issue is fixed in i18next-http-middleware 3.9.7 and i18next-fs-backend 2.6.6.

Affected products

  • i18next i18next-http-middleware <= 3.9.6

Identifiers

  • CVE-2026-48714
  • GHSA-f49m-vf83-692w

Timeline

  • 2026-05-22: patched: Fix released in version 3.9.7
  • 2026-06-15: disclosed: NVD publication date
  • 2026-06-25: advisory: GitHub Advisory published

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.