CVE-2026-44573
From 12.2.0 to before 15.5.16 and 16.2.5, Applications using the Pages Router with i18n configured and middleware/proxy-based authorization can allow unauthorized access to protected page data through locale-less /_next/data/<buildId>/<page>.json…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.62%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
Next.js is a React framework for building full-stack web applications. From 12.2.0 to before 15.5.16 and 16.2.5, Applications using the Pages Router with i18n configured and middleware/proxy-based authorization can allow unauthorized access to protected page data through locale-less /_next/data/<buildId>/<page>.json requests. In affected configurations, middleware does not run for the unprefixed data route, allowing an attacker to retrieve SSR JSON for protected pages without passing the intended authorization checks. This vulnerability is fixed in 15.5.16 and 16.2.5.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- EPSS
- 0.62% probability · 48th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-863, CWE-551
- Affected
- vercel/next.js
- Source
- security-advisories@github.com
References
- https://github.com/vercel/next.js/security/advisories/GHSA-36qx-fr4f-26g5Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:34608
- https://access.redhat.com/errata/RHSA-2026:37272
- https://access.redhat.com/errata/RHSA-2026:40974
- https://access.redhat.com/errata/RHSA-2026:54435
- https://access.redhat.com/security/cve/CVE-2026-44573
- https://bugzilla.redhat.com/show_bug.cgi?id=2477199
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44573.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.