CVE-2026-41683: high-severity vulnerability in i18next-http-middleware
HTTP response splitting and DoS in i18next-http-middleware via unsanitised Content-Language header
Published
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 8.6epss 0.4%
exploitation probability
0.4%top 68% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L
Affected products
i18next · i18next-http-middlewareRelated CVEs — i18next-http-middleware
In the same product, most dangerous first.
CVE-2026-48714CRITICALi18next-http-middleware missingKeyHandler does not reject keys whose segments contain prototype-polluting namesEPSS 0.7%CVE-2026-41690HIGHPrototype pollution and path traversal in i18next-http-middleware via user-controlled language and namespace parametersEPSS 0.5%CVE-2026-42353HIGHPath traversal / SSRF in i18next-http-middleware via user-controlled language and namespace parametersEPSS 0.4%