CVE-2026-40299

Описание

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.

A flaw was found in next-intl, a library for internationalization in Next.js applications. A remote attacker could exploit this vulnerability in applications using the next-intl middleware with localePrefix: 'as-needed'. By crafting specific URLs, the attacker could cause the middleware to redirect a user's browser to an arbitrary external website, even if the user initially started from a trusted application URL. This could lead to users being unknowingly directed to malicious sites.