What is CVE-2026-44573?

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/ / .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.

How severe is CVE-2026-44573?

CVE-2026-44573 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-44573 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-44573?

CVE-2026-44573 affects Vercel Next.js. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-44573?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-44573 have an EU (EUVD) identifier?

Yes. CVE-2026-44573 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30057.

When was CVE-2026-44573 published?

CVE-2026-44573 was published on 2026-05-13 and last updated on 2026-07-03.

CVE-2026-44573

CVE-2026-44573 is a high-severity vulnerability in Vercel Next.js with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-863.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (42nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-30057
Weakness: CWE-863
Affected product: Vercel Next.js
Published: 2026-05-13
Last modified: 2026-07-03

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.

Frequently asked questions

What is CVE-2026-44573?: 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.
How severe is CVE-2026-44573?: CVE-2026-44573 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-44573 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-44573?: CVE-2026-44573 affects Vercel Next.js. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-44573?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-44573 have an EU (EUVD) identifier?: Yes. CVE-2026-44573 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-30057.
When was CVE-2026-44573 published?: CVE-2026-44573 was published on 2026-05-13 and last updated on 2026-07-03.

References

Affected products (1)

cpe:2.3:a:vercel:next.js:*:*:*:*:*:node.js:*:*

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