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CVE Record

CVE-2026-44575: Next.js: Middleware / Proxy bypass in App Router applications via segment-prefetch routes

Next.js is a React framework for building full-stack web applications. From 15.2.0 to before 15.5.16 and 16.2.5, App Router applications that rely on middleware or proxy-based checks for authorization can allow unauthorized access through transport-specific route variants used for segment prefetching. In affected configurations, specially crafted .rsc and segment-prefetch URLs can resolve to the same page without being matched by the intended middleware rule, which can allow protected content to be reached without the expected authorization check. This vulnerability is fixed in 15.5.16 and 16.2.5.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in Next.js lets attackers reach protected pages by requesting special prefetch variants of a URL that middleware-based authorization checks fail to inspect. Sites that rely on Next.js middleware to gate access to internal or paid content could expose that content to unauthenticated visitors until the app is upgraded.

Executive priority

Priority: High. Schedule upgrades this sprint for any Next.js App Router site that gates content with middleware. No confirmed exploitation, but the bypass is network-reachable, unauthenticated, and vendor-confirmed, so exposure of protected data is plausible until patched.

Technical view

In App Router apps on Next.js 15.2.0–15.5.15 and 16.0.0–16.2.4, `.rsc` and segment-prefetch URL variants resolve to the same page but are not matched by the middleware rule intended to enforce authorization. This bypass (CWE-288/CWE-551) allows protected route content to be served without the expected proxy or middleware check. Fixed in 15.5.16 and 16.2.5.

Likely exposure

Any internet-facing Next.js App Router deployment on 15.2.0–15.5.15 or 16.0.0–16.2.4 that uses middleware or an upstream proxy rule to enforce authentication or authorization on protected routes. Static-only sites and pages not gated by middleware are not exposed.

Exploitation context

CVSS 7.5 (AV:N/AC:L/PR:N/UI:N, confidentiality High). Not listed in CISA KEV and no public exploitation reports are cited in the source bundle. Vercel issued a confirmed GHSA advisory and Red Hat has shipped errata, indicating vendor-verified impact and a straightforward network-based attack surface.

Researcher notes

Root cause per GHSA-267c-6grr-h53f is a mismatch between middleware route matching and the transport-specific URL variants Next.js uses for React Server Component segment prefetching. Middleware sees the prefetch URL as unmatched, but the runtime still resolves it to the protected page. Focus tests on any middleware that uses path-based matchers for auth; defense-in-depth belongs in the route handler or layout, not solely in middleware.

Mitigation direction

  • Upgrade Next.js to 15.5.16 (15.x line) or 16.2.5 (16.x line) across all affected apps.
  • Apply Red Hat errata RHSA-2026:37272 and RHSA-2026:34608 on impacted RHEL-based deployments.
  • Where upgrade is delayed, add authorization checks inside server components or route handlers rather than relying solely on middleware.
  • Inventory Next.js versions in CI, container images, and third-party services to confirm no vulnerable builds remain.
  • Review CDN/WAF rules to block or normalize `.rsc` and segment-prefetch URL variants against sensitive paths as a temporary control.

Validation and detection

  • Query package manifests and lockfiles for `next` versions and flag anything below 15.5.16 or between 16.0.0 and 16.2.5.
  • Request each protected route with and without the `.rsc` suffix and typical segment-prefetch headers, confirming both are blocked when unauthenticated.
  • Review middleware matchers to ensure they cover all transport variants of protected paths, not just the canonical URL.
  • Check server access logs for anomalous `.rsc` or prefetch requests to authenticated routes prior to remediation.
  • After patching, re-run authorization test suites and confirm the GHSA-267c-6grr-h53f advisory shows resolved for deployed builds.
Prepared
Confidence
high
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-288: Exact CWE lookup

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cwe · low confidence lookup

CWE-551: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-44575 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
7Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-44575Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPnext.js: Next.js: Unauthorized access to protected content via middleware bypass
other:Red Hat severity ratingcvssV3_1
  • 2026-05-13T18:01:17.168Z: Reported to Red Hat.
  • 2026-05-13T16:54:39.455Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
vercelnext.js>= 16.0.0, < 16.2.5, >= 15.2.0, < 15.5.16Listed
Weakness

CWE details

CWE-288CWE-551

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.