CVE-2026-40299
next-intl has an open redirect vulnerability
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]`.
INFO
Published Date :
April 17, 2026, 9:16 p.m.
Last Modified :
Oct. 26, 2026, 9:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update next-intl to version 4.9.1 or later.
- Review middleware configuration for localePrefix settings.
- Test URL handling and redirect behavior.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-40299.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-40299 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-40299
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-40299 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-40299 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Translated by [email protected]
Oct. 26, 2026
Action Type Old Value New Value Added Translation Title: next-intl de amannn, Description: next-intl proporciona internacionalización para Next.js. Las aplicaciones que utilizan el middleware “next-intl” antes de la versión 4.9.1 con “localePrefix: ’as-needed’” podrían construir URLs donde el manejo de rutas y el analizador de URLs WHATWG resolvían un objetivo de redirección relativo a otro host (por ejemplo, “//” relativo al esquema o caracteres de control eliminados por el analizador de URLs), por lo que el middleware podría redirigir el navegador fuera del sitio mientras el usuario aún partía de una URL de aplicación de confianza. El problema ha sido parcheado en “[email protected]”. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'amannn', 'product': 'next-intl', 'versions': [{'status': 'affected', 'version': '< 4.9.1'}]}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-40299', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-04-20T15:56:01.407919Z'} -
New CVE Received by [email protected]
Apr. 17, 2026
Action Type Old Value New Value Added 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]`. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-601 Added Reference https://github.com/amannn/next-intl/commit/1c80b668aa6d853f470319eec10a3f61e78a70e6 Added Reference https://github.com/amannn/next-intl/pull/2304 Added Reference https://github.com/amannn/next-intl/releases/tag/v4.9.1 Added Reference https://github.com/amannn/next-intl/security/advisories/GHSA-8f24-v5vv-gm5j