Path traversal / URL injection via unsanitised lng/ns/projectId/version in i18next-locize-backend

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

i18next-locize-backend is a simple i18next backend for locize.com which can be used in Node.js, in the browser and for Deno. Prior to version 9.0.2, i18next-locize-backend interpolates lng, ns, projectId, and version directly into the configured loadPath / privatePath / addPath / updatePath / getLanguagesPath URL templates with no path-component validation and no encoding. When an application exposes any of these values to user-controlled input (?lng= / ?ns= query parameters via i18next-browser-languagedetector, cookies, request headers, or a URL-derived projectId), a crafted value can change the structure of the outgoing request URL. Affected call sites in lib/index.js (pre-patch): the interpolate() helper is used at the five URL-build sites — _readAny/read (line 415 for private, 426 for public), getLanguages (lines 271 and 296), and writePage (lines 616 and 622) for the missing-key and update POST paths. The helper interpolate in lib/utils.js substitutes raw values with no encoding. This issue has been patched in version 9.0.2.

Source published

8 May 2026 15:41:14 UTC

Source modified

8 May 2026 16:06:11 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

i18next-locize-backend is a simple i18next backend for locize.com which can be used in Node.js, in the browser and for Deno. Prior to version 9.0.2, i18next-locize-backend interpolates lng, ns, projectId, and version directly into the configured loadPath / privatePath / addPath / updatePath / getLanguagesPath URL templates with no path-component validation and no encoding. When an application exposes any of these values to user-controlled input (?lng= / ?ns= query parameters via i18next-browser-languagedetector, cookies, request headers, or a URL-derived projectId), a crafted value can change the structure of the outgoing request URL. Affected call sites in lib/index.js (pre-patch): the interpolate() helper is used at the five URL-build sites — _readAny/read (line 415 for private, 426 for public), getLanguages (lines 271 and 296), and writePage (lines 616 and 622) for the missing-key and update POST paths. The helper interpolate in lib/utils.js substitutes raw values with no encoding. This issue has been patched in version 9.0.2.

Source published

May 8, 2026, 3:41:14 PM (timezone not stated)

Source modified

May 8, 2026, 4:06:11 PM (timezone not stated)

Observed here

7 Nov 2026 10:41:01 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

i18next-locize-backend is a simple i18next backend for locize.com which can be used in Node.js, in the browser and for Deno. Prior to version 9.0.2, i18next-locize-backend interpolates lng, ns, projectId, and version directly into the configured loadPath / privatePath / addPath / updatePath / getLanguagesPath URL templates with no path-component validation and no encoding. When an application exposes any of these values to user-controlled input (?lng= / ?ns= query parameters via i18next-browser-languagedetector, cookies, request headers, or a URL-derived projectId), a crafted value can change the structure of the outgoing request URL. Affected call sites in lib/index.js (pre-patch): the interpolate() helper is used at the five URL-build sites — _readAny/read (line 415 for private, 426 for public), getLanguages (lines 271 and 296), and writePage (lines 616 and 622) for the missing-key and update POST paths. The helper interpolate in lib/utils.js substitutes raw values with no encoding. This issue has been patched in version 9.0.2.

Source published

8 May 2026 16:16:11 UTC

Source modified

26 Oct 2026 18:10:00 UTC

Observed here

27 Oct 2026 10:10:19 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

### Summary Versions of `i18next-locize-backend` prior to 9.0.2 interpolate `lng`, `ns`, `projectId`, and `version` directly into the configured `loadPath` / `privatePath` / `addPath` / `updatePath` / `getLanguagesPath` URL templates with no path-component validation and no encoding. When an application exposes any of these values to user-controlled input (`?lng=` / `?ns=` query parameters via `i18next-browser-languagedetector`, cookies, request headers, or a URL-derived `projectId`), a crafted value can change the structure of the outgoing request URL. Affected call sites in `lib/index.js` (pre-patch): the `interpolate()` helper is used at the five URL-build sites — `_readAny`/`read` (line 415 for private, 426 for public), `getLanguages` (lines 271 and 296), and `writePage` (lines 616 and 622) for the missing-key and update POST paths. The helper `interpolate` in `lib/utils.js` substitutes raw values with no encoding. ### Impact An attacker who can influence `lng`, `ns`, `projectId`, or `version` can: - **Path traversal** — `lng = '../../admin'` against `https://api.locize.app/{{projectId}}/{{version}}/{{lng}}/{{ns}}` changes the request URL path segment that reaches the locize CDN / API. - **Query-string injection** — `lng = 'en?x=y'` appends an attacker-chosen query to the URL. - **Fragment truncation** — `lng = 'en#x'` silently truncates the path in browser fetches. - **URL-encoded bypass** — `lng = 'en%2F..'` leverages server-side decoding to reintroduce `/..`. The worst-case concrete impact is loading an unintended translation resource (potentially causing wrong content to render) and, when a custom `loadPath` is configured against an internal / file-scheme URL, **SSRF or arbitrary-file read** on the host running the backend. Additionally, the pre-patch `interpolate()` function read `data[key]` without excluding prototype-chain properties — under prototype-pollution conditions in the same process, that path could pull values from `Object.prototype` into the URL. ### Related fixes shipped in 9.0.2 - The `defaults()` helper replaces `for...in` iteration with `Object.keys()` plus an explicit prototype-key guard so a polluted `Object.prototype` cannot leak into the merged options object. - New `utils.interpolateUrl` / `isSafeUrlSegment` / `sanitizeLogValue` / `redactUrlCredentials` helpers mirror the pattern shipped in `[email protected]` (see its advisory [GHSA-q89c-q3h5-w34g](https://github.com/i18next/i18next-http-backend/security/advisories/GHSA-q89c-q3h5-w34g)). ### Affected versions All versions of `i18next-locize-backend` prior to **9.0.2**. ### Patch Fixed in **9.0.2**. `lib/index.js` now uses `interpolateUrl()` at every URL-build site and returns an error callback (or silently drops the queued write for `writePage`) when any interpolated value fails the safety check. Legitimate i18next language-code shapes (BCP-47, `en_US`, `zh-Hant-HK`, `my-custom.ns`, `+`-joined multi-language values) all pass. ### Workarounds No workaround short of upgrading. If you cannot upgrade immediately, sanitise `lng` / `ns` / `projectId` / `version` at your application boundary before passing them through to i18next — reject values containing `..`, `/`, `\`, `?`, `#`, `%`, whitespace, control characters, and cap the length. ### Credits Discovered via an internal security audit of the i18next / locize ecosystem. ### References - [CWE-22: Path Traversal](https://cwe.mitre.org/data/definitions/22.html) - [CWE-74: Injection](https://cwe.mitre.org/data/definitions/74.html) - [CWE-1321: Prototype Pollution (amplification path)](https://cwe.mitre.org/data/definitions/1321.html) - Related advisory in the same ecosystem: [GHSA-q89c-q3h5-w34g (i18next-http-backend)](https://github.com/i18next/i18next-http-backend/security/advisories/GHSA-q89c-q3h5-w34g)

Source published

22 Apr 2026 20:28:27 UTC

Source modified

13 May 2026 13:52:30 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Publisher rating · MODERATE