Threats affecting pkg:npm/next-intl

A prototype pollution vulnerability exists in next-intl versions prior to 4.9.2 when using the experimental.messages.precompile feature. An attacker can craft a JSON translation catalog containing a top-level __proto__ key, which causes the build process to assign properties onto Object.prototype. This pollution affects all objects during the Next.js build, potentially enabling tampering with build tool internals and generated bundles. The vulnerability arises from improper handling of nested keys in setNestedProperty, which does not block reserved prototype keys. The issue is fixed in version 4.9.2.

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`.