GHSA-4C35-WCG5-MM9H next-intl has prototype pollution with `experimental.messages.precompile` via attacker-controlled translation catalog keys

Summary setNestedProperty in packages/next-intl/src/extractor/utils.tsx walks a dotted key path and assigns the final value without blocking the reserved keys proto, constructor, or prototype. When the next-intl Next.js plugin is configured with experimental.messages and messages.precompile: true...

Prototype Pollution

Overview next-intl is an Internationalization i18n for Next.js Affected versions of this package are vulnerable to Prototype Pollution in the setNestedProperty function when processing translation catalog keys containing reserved properties such as proto, constructor, or prototype. An attacker ca...

CVE-2026-40299

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...

CVE-2026-40299 next-intl has an open redirect vulnerability

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...

CVE-2026-40299

The CVE-2026-40299 issue affects the next-intl library used with Next.js. The vulnerability arises in the middleware when localePrefix: 'as-needed' is enabled, allowing URL handling and the WHATWG URL parser to resolve a relative redirect target to another host. This can cause the browser to be r...

CVE-2026-40299 next-intl has an open redirect vulnerability

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...

Open Redirect

Overview next-intl is an Internationalization i18n for Next.js Affected versions of this package are vulnerable to Open Redirect in the middleware process when localePrefix is set to 'as-needed'. An attacker can redirect users to an external site by crafting URLs that exploit the way relative...

PT-2026-32979

Name of the Vulnerable Software and Affected Versions next-intl versions prior to 4.9.1 Description Applications using the middleware with localePrefix: 'as-needed' could construct URLs where path handling and the WHATWG URL parser resolved a relative redirect target to another host. This occurs...