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Vulnerabilities

Vulnerability · CVE-2026-41683

i18next-http-middleware is a middleware to be used with Node.js web frameworks like express or Fastify and also for Deno.

Published May 8, 2026 · catalog updated Jun 17, 2026 · i18next-http-middleware is a middleware

Check if you run it

No confirmed exploitation is on record for CVE-2026-41683. EPSS is 0.40%. Act only if a listed version of i18next-http-middleware is a middleware is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (i18next-http-middleware is a middleware).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.6
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.40%
Remediation
Version ranges on file
Affected products
stated named in the record

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • stated named in the record< 19.5.0

How to fix CVE-2026-41683

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-41683. EPSS is 0.40%. Act only if a listed version of i18next-http-middleware is a middleware is installed.

Which versions are affected?

Compare what you have installed with named in the record < 19.5.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-113; CWE-79: Cross-site Scripting (XSS). EPSS 0.40%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. May 8, 2026 · NIST NVD

    Detected

    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

  2. Jun 17, 2026 · NIST NVD

    Updated

    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

Sources

  • CVE.orgVulnerability recordCVE-2026-41683

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-41683

    30-day exploitation probability 0.4%

    first.org
  • NIST NVDVulnerability recordCVE-2026-41683

    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 uti

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.