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Medium · 6.9 CVE-2026-40299 EUVD-2026-23543GHSA-8f24-v5vv-gm5j

next-intl has an open redirect vulnerability

Published Apr 17, 2026 · Updated Apr 20, 2026 · Assigned by GitHub_M

Description

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 products

VendorProductAffectedFixed
amannn next-intl < 4.9.1 —

Affected packages

EcosystemPackageAffectedFixedRecord
npm next-intl < 4.9.1 4.9.1 GHSA-8f24-v5vv-gm5j

References