CVE-2026-6270

CRITICALNVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under NVD CVSS v3. EPSS exploit probability: 0.5%, top 60% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

@fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances. When a Fastify application registers authentication middleware in a parent scope and then registers child plugins with @fastify/middie, the child scope does not inherit the parent middleware. This allows unauthenticated requests to reach routes defined in child plugin scopes, bypassing authentication and authorization checks. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds.

CVSS v3
9.1
EG Score
9.1(medium)
EG Risk
57(Track*)
EG Risk 57/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
41%
KEV
Not listed

Published

April 16, 2026

Last Modified

May 14, 2026

Advisory Details (3)

Auto-updated Aug 1, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available

@fastify/middie vulnerable to middleware authentication bypass in child plugin scopes · Advisory · fastify/middie · GitHub

https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5w
github Patch Available🟡 PoC Available

Middleware path doubling causes authentication bypass in child plugin scopes · Advisory · fastify/fastify-express · GitHub

https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
@fastify/middie—9.3.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 4× in last 7d / 26× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 152 total refreshes for this CVE.

  1. 2026-09-15 03:12 UTCEPSS rescore
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  1. 2026-08-16 14:56 UTCEPSS rescore
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  46. 2026-07-20 18:02 UTCOSV refresh
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  75. 2026-07-01 15:07 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-6270?
CVE-2026-6270 is a critical vulnerability published on April 16, 2026. @fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances. When a Fastify application registers authentication middleware in a parent scope and then registers child plugins with @fastify/middie, the child scope does not inherit the…
When was CVE-2026-6270 disclosed?
CVE-2026-6270 was first published in the National Vulnerability Database on April 16, 2026, with the most recent update on May 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-6270 actively exploited?
CVE-2026-6270 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 58.8% of all scored CVEs.
What is the CVSS score of CVE-2026-6270?
CVE-2026-6270 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-6270?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-6270, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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