CVE-2026-40299
Medium
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 `[email protected]`.
SeverityMedium
CVSS6.9
Exploit probability—
ProductNext-intl
PublishedApr 17, 2026
First seenApr 17, 2026
Weakness typeCWE-601Open redirect
How to fix
Update
- next-intl4.9.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| next-intlnpm | v < 4.9.1 | 4.9.1 |
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