How severe is CVE-2026-44573?

CVE-2026-44573 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-44573?

CVE-2026-44573 affects the following packages: next (npm), next (npm). Ecosystems affected: npm.

How do I fix CVE-2026-44573?

Update next to 15.5.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44573 is resolved across your whole dependency graph.

How do I detect CVE-2026-44573 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for next, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-44573 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-44573 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-44573 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-44573?

CVE-2026-44573 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 57th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-44573?

CVE-2026-44573 is classified as CWE-863 (CWE-863), CWE-551 (CWE-551). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-44573 published, and has it been updated?

CVE-2026-44573 was published on May 13, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

HIGH severity

CVE-2026-44573 — next

HIGH

CVE-2026-44573 is a high-severity (CVSS 7.5) CWE-863 vulnerability in next. A fix is available for next — see the affected versions and patch details below.

Next.js: Middleware / Proxy bypass in Pages Router applications using i18n

Also known asGHSA-36qx-fr4f-26g5

Published

May 13, 2026

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44573.

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs57th percentile — riskier than 57% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

61Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

nextnpm

91.9Mdownloads / week

Description

Impact

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.

Fix

The matcher logic was updated to perform the same match as it would on a non-i18n data route.

Workarounds

If you cannot upgrade immediately, enforce authorization in the page's server-side data path instead of relying solely on middleware.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`next`	≥ 12.2.0&&< 15.5.16	15.5.16`npm install next@15.5.16`
📦npm	`next`	≥ 16.0.0&&< 16.2.5	16.2.5`npm install next@16.2.5`

Affected Products

1 product · 2 configurations

Application

next.jsvercel

≥ 16.0.0 && < 16.2.5

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for next, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update next to 15.5.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44573 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Important: A flaw in Next.js applications allows unauthorized access to sensitive server-side rendered (SSR) JSON data by bypassing middleware authorization checks. This occurs when applications use the Pages Router with internationalization (i18n) and middleware or proxy-based authorization, enabling remote attackers…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for CVE-2026-44573 (CC BY 4.0)

Product	Fixed in	Advisory
Streams for Apache Kafka 2.9.4	`next`	RHSA-2026:34608
Streams for Apache Kafka 3.2.1	`next`	RHSA-2026:54435
Red Hat Trusted Artifact Signer 1.3	`rhtas/rekor-search-ui-rhel9:1783958622`	RHSA-2026:40974
Red Hat Trusted Artifact Signer 1.4	`rhtas/rekor-search-ui-rhel9:1783327185`	RHSA-2026:37272

Frequently Asked Questions

### Impact 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. ### Fix The matcher logic was updated to perform the same match as it would on a non-i18n data route. ### Workarounds If you cannot upgrade immediately, enforce authoriza

O3 Security · Impact-Aware SCA

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