High Access control

CVE-2026-44573 — Next.js: Middleware / Proxy bypass in Pages Router applications using i18n

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.

Published May 13, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.8% (30-day exploitation probability)+8
Technical severity (high)+6
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.76%

ahead of 54% of scored CVEs · Oct 14, 2026

Affects

Vercel

Next.js

CVSS base

7.5

High · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Vercel Next.js).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (access control), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Vercel	Next.js	≥ 12.2.0 and < 15.5.16≥ 16.0.0 and < 16.2.5	Vulnerable	NIST National Vulnerability Database
Vercel	Next.js	version >= 12.2.0, < 15.5.16version >= 16.0.0, < 16.2.5	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
7.5	CVSS 3.1	High	3.9	3.6	security-advisories@github.com via NIST National Vulnerability Database
7.5	CVSS 3.1	High	3.9	3.6	0b0ca135-0b70-47e7-9f44-1890c2a1c46c via NIST National Vulnerability Database
7.5	CVSS 3.1	High	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-863 · Incorrect Authorization

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.76%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Audit administrative actions and access to resources outside each user’s normal pattern.

web/proxy/WAF logsnetwork IDS/IPSauthentication logsapplication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · vercel/next.js
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 7.5
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Modified
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
May 13, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

8 on the record

github.com/vercel/next.js/security/advisories/GHSA-36qx-fr4f-26g5
Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
access.redhat.com/errata/RHSA-2026:40974
NIST National Vulnerability Database
bugzilla.redhat.com/show_bug.cgi
NIST National Vulnerability Database
access.redhat.com/errata/RHSA-2026:37272
NIST National Vulnerability Database
access.redhat.com/security/cve/CVE-2026-44573
NIST National Vulnerability Database
access.redhat.com/errata/RHSA-2026:54435
NIST National Vulnerability Database
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44573.json
NIST National Vulnerability Database
access.redhat.com/errata/RHSA-2026:34608
NIST National Vulnerability Database

Elsewhere on this site

Vercel
every CVE for this vendor

Access control
same class

CWE-863
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-94543 Next.js: Cache poisoning of SSG and ISR pages in self-hosted Next.js applications 13d
Medium CVE-2026-94483 Next.js: Server-Side Request Forgery in Image Optimization 13d
High CVE-2026-45109 Next.js: Middleware / Proxy bypass in App Router applications via segment-prefetch routes May 13, 2026
Low CVE-2026-44582 Next.js: Cache poisoning via collisions in React Server Component cache-busting May 13, 2026
High CVE-2026-44579 Next.js: Denial of Service via connection exhaustion in applications using Cache Components May 13, 2026
Medium CVE-2026-44580 Next.js: Cross-site scripting in beforeInteractive scripts with untrusted input May 13, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-44573 is "Next.js: Middleware / Proxy bypass in Pages Router applications using i18n", rated High. It affects Next.js (Vercel); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.76% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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