CVE-2026-40299
CWE-601Published: April 17, 2026· Updated: Apr 20, 2026
Official 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]`.
Technical Analysis
CVE-2026-40299 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.
CVSS v3.1 Vector Breakdown
Exploit & PoC Resources
All References (4)
Quick Facts
Related CVEs (CWE-601)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-40299 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts