CVE-2026-40299

Summary

next-intl provides internationalization for Next.js. Applications using the next-intl middleware prior to version 4.9.1with localePrefix: 'as-needed' could construct URLs where path handling and the WHATWG URL parser resolved a relative redirect target to another host (e.g. scheme-relative // or control characters stripped by the URL parser), so the middleware could redirect the browser off-site while the user still started from a trusted app URL. The problem has been patchedin next-intl@4.9.1.

Affected Software

VendorProductVersion RangeStatus
amannnnext-intl< 4.9.1affected

Weaknesses

  • CWE-601: CWE-601: URL Redirection to Untrusted Site ('Open Redirect')

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: yes
    • Technical Impact: partial

References