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Full vulnerability report · 2026
CVE-2026-94486High confidence

Next.js: Information disclosure in the Next.js development server's Model Context Protocol endpoint

vercel · next.js

Official source article: GitHub GHSA-39W2-RJM5-CHCV ↗. Check the applicable product and release in the original source.

2.3LowCVSS 4.0
Recommended action
Patch only the product branches with a verified fix

Low technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 20 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityLowOperational priority:Low, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.11% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs vercel next.js and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: No default targetRemediation target: Normal maintenance

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 20 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Open-source package ranges2 source-attributed ranges

These OSV and GitHub advisory ranges apply only to the named package and ecosystem. A listed fixed version is not a universal product patch or proof that an update is installed.

Ecosystem and packageAffected rangeFirst fixed versionEvidence
npmnext>= 16.0.0, < 16.3.816.3.8GitHub advisory ↗upstream repository advisory · 7 Oct 2026
npmnextSEMVER: introduced 16.0.0; fixed 16.3.816.3.8OSV record ↗aggregator derived · 7 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-94486 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitynext: Next.js: Information disclosure via unrestricted cross-site requests
20 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • firefox as a component of Red Hat Enterprise Linux 10
  • firefox.src as a component of Red Hat Enterprise Linux 10
  • thunderbird as a component of Red Hat Enterprise Linux 10
  • thunderbird.src as a component of Red Hat Enterprise Linux 10
  • firefox as a component of Red Hat Enterprise Linux 7
  • firefox.src as a component of Red Hat Enterprise Linux 7
  • firefox as a component of Red Hat Enterprise Linux 8
  • firefox.src as a component of Red Hat Enterprise Linux 8
  • thunderbird as a component of Red Hat Enterprise Linux 8
  • thunderbird.src as a component of Red Hat Enterprise Linux 8
  • firefox as a component of Red Hat Enterprise Linux 9
  • firefox-x11 as a component of Red Hat Enterprise Linux 9
Summary
A flaw was found in Next.js. The local development server exposes a Model Context Protocol (MCP) endpoint without properly restricting cross-site requests. If a developer running the development server visits a malicious website, an attacker can issue unauthorized requests to this endpoint, leading to sensitive information disclosure. This flaw allows unauthorized access to local project file locations, source code snippets from error reports, application route inventories, and development logs.
Remediation
Fix deferred
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-91667

No EUVD known-exploited evidence

Next.js has information disclosure in development server's Model Context Protocol endpoint

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
2.3 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

Low technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority. Verified remediation exists for at least one product or source, but 20 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

Next.js is a React framework for building full-stack web applications. From 16.0.0 until 16.3.8, the next dev development server exposes a Model Context Protocol endpoint without reliably restricting cross-site requests. A malicious website visited by a developer can reach the endpoint and read the project's disk location, source code snippets from error reports, route inventory, and development logs. Production deployments do not serve this endpoint. This issue is fixed in version 16.3.8.

What

Next.js is a React framework for building full-stack web applications. From 16.0.0 until 16.3.8, the next dev development server exposes a Model Context Protocol endpoint without reliably restricting cross-site requests. A malicious website visited by a developer can reach the endpoint and read the project's disk location, source code snippets from error reports, route inventory, and development logs. Production deployments do not serve this endpoint. This issue is fixed in version 16.3.8.

Why

The product does not properly verify that the source of data or communication is valid.

How

An attacker operating through a network path may attempt exploitation when the stated preconditions are met. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

Next.js is a React framework for building full-stack web applications. From 16.0.0 until 16.3.8, the next dev development server exposes a Model Context Protocol endpoint without reliably restricting cross-site requests. A malicious website visited by a developer can reach the endpoint and read the project's disk location, source code snippets from error reports, route inventory, and development logs. Production deployments do not serve this endpoint. This issue is fixed in version 16.3.8.

Why

The product does not properly verify that the source of data or communication is valid.

How

An attacker operating through a network path may attempt exploitation when the stated preconditions are met. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Origin Validation Error → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
Passive interaction required
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-346 ↗

CWE-346: Origin Validation Error. The product does not properly verify that the source of data or communication is valid.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATPresentAttack requirements: A particular deployment or execution condition must be present.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIPassiveUser interaction: A user must unknowingly interact with the vulnerable system.VCLowVulnerable-system confidentiality: A successful attack can cause a limited loss.VILowVulnerable-system integrity: A successful attack can cause a limited loss.VANoneVulnerable-system availability: No direct loss is represented by this metric.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-346
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-91667Official EUVD mapping

Next.js has information disclosure in development server's Model Context Protocol endpoint

Official EUVD record ↗
BSI · German · WID-SEC-2026-3699Vercel Next.js: Mehrere Schwachstellen

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Vercel Next.js ausnutzen, um vertrauliche Informationen offenzulegen, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren oder Denial-of-Service-Zustände auszulösen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20261007Security Bulletin 7 Oct 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 7 Oct 2026, published on 7 October 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-036541Vercel, Inc. (旧 Zeit, Inc.)のNext.jsにおける同一生成元ポリシー違反に関する脆弱性

Next.jsはフルスタックのウェブアプリケーションを構築するためのReactフレームワークです。バージョン16.0.0から16.3.8までの間、next dev開発サーバーはModel Context Protocolエンドポイントを適切にクロスサイトリクエストから制限せずに公開していました。開発者が訪問した悪意のあるウェブサイトはこのエンドポイントにアクセスでき、プロジェクトのディスク上の場所やエラー報告からのソースコードの断片、ルート情報、開発ログを読み取る可能性があります。本番環境へデプロイした場合はこのエンドポイントが提供されません。この問題はバージョン16.3.8で修正されました。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
Fixed
16.3.8.
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
Official vendor articles2 stored documents

Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.

04

Evidence and provenance

Published 2 Oct 2026 · Last source change 2 Oct 2026, 16:20 UTC · CWE-346 · Origin Validation Error

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-10-03
European sourceENISA EUVD · EUVD-2026-91667
Product sourceVendor CSAF · Red Hat Product Security
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. BlackTree coverageBlackTree article coverage changed from 1 BlackTree article to 1 BlackTree article.
    Before
    1 BlackTree article
    After
    1 BlackTree article
    BlackTree editorial ↗
  2. ENISA EUVD mappingEUVD-2026-91667 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-91667"}
    ENISA EUVD ↗
  3. Vendor guidanceAuthoritative vendor guidance changed: added patch: github.com/2d9f50a409312696145b82b3157aadb6b1fef476; added remediation: github.com/2d9f50a409312696145b82b3157aadb6b1fef476; removed remediation: github.com/GHSA-39w2-rjm5-chcv; 1 further additions.
    Before
    remediation: github.com/GHSA-39w2-rjm5-chcv
    After
    patch: github.com/2d9f50a409312696145b82b3157aadb6b1fef476 · remediation: github.com/2d9f50a409312696145b82b3157aadb6b1fef476 · vendor advisory: github.com/GHSA-39w2-rjm5-chcv
    security-advisories@github.com ↗
  4. Vendor guidanceAuthoritative vendor guidance changed: added remediation: github.com/GHSA-39w2-rjm5-chcv; removed remediation: wid.cert-bund.de/securityadvisory?name=WID-SEC-2026-3699.
    Before
    remediation: wid.cert-bund.de/securityadvisory?name=WID-SEC-2026-3699
    After
    remediation: github.com/GHSA-39w2-rjm5-chcv
    CNA ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    Vercel Next.js <16.3.8; Vercel Next.js <15.5.27 · Fixed: No fixed version is explicitly recorded in this authority advisory.
    After
    next.js: >= 16.0.0, < 16.3.8 · Fixed: 16.3.8.
    CNA ↗
  6. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    CNA ↗
  7. SeveritySeverity changed from Unknown to Low.
    Before
    Unknown
    After
    Low
    CNA ↗
  8. CVSS scoreCVSS score changed from not recorded to 2.3 (CVSS 4.0 · CNA · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N).
    Before
    not recorded
    After
    2.3 (CVSS 4.0 · CNA · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N)
    CNA ↗
  9. BlackTree coverageBlackTree article coverage changed from no BlackTree article to 1 BlackTree article.
    Before
    no BlackTree article
    After
    1 BlackTree article
    BlackTree editorial ↗
  10. Catalogue recordCVE added to the BlackTree catalogue.
    Official national cybersecurity authority ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-91667↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference · GitHub GHSA-39W2-RJM5-CHCV↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-94486 · cve.blacktree.nl