i18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Prior to version 3.9.3, i18next-http-middleware wrote user-controlled language values into the Content-Language response header after passing them through utils.escape(), which is an HTML-entity encoder that does not strip carriage return, line feed, or other control characters. When the application used an older i18next (< 19.5.0) that still exercised the backward-compatibility fallback at LanguageDetector.js:100 or otherwise produced a raw detected value, CRLF sequences in the attacker-controlled lng parameter reached res.setHeader('Content-Language', ...) verbatim. This issue has been patched in version 3.9.3.

Project Subscriptions

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-c3h8-g69v-pjrg i18next-http-middleware: HTTP response splitting and DoS via unsanitised Content-Language header
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Sat, 09 May 2026 00:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 08 May 2026 16:00:00 +0000

Type Values Removed Values Added
Description i18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno. Prior to version 3.9.3, i18next-http-middleware wrote user-controlled language values into the Content-Language response header after passing them through utils.escape(), which is an HTML-entity encoder that does not strip carriage return, line feed, or other control characters. When the application used an older i18next (< 19.5.0) that still exercised the backward-compatibility fallback at LanguageDetector.js:100 or otherwise produced a raw detected value, CRLF sequences in the attacker-controlled lng parameter reached res.setHeader('Content-Language', ...) verbatim. This issue has been patched in version 3.9.3.
Title HTTP response splitting and DoS in i18next-http-middleware via unsanitised Content-Language header
Weaknesses CWE-113
CWE-79
References
Metrics cvssV3_1

{'score': 8.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-08T23:29:00.230Z

Reserved: 2026-04-22T03:53:24.406Z

Link: CVE-2026-41683

cve-icon Vulnrichment

Updated: 2026-05-08T23:28:52.247Z

cve-icon NVD

Status : Received

Published: 2026-05-08T16:16:11.320

Modified: 2026-05-08T16:16:11.320

Link: CVE-2026-41683

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-08T19:45:15Z

Weaknesses