CVE-2026-6270@fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances.
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No exploitation reported and no EPSS estimate yet.
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@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
- 9.1 CRITICAL (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weakness (CWE)
- CWE-436
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
fastify fastify/middie fastify:fastify/middie | before 9.3.2 | NVD |
References
- https://cna.openjsf.org/security-advisories.htmlvendor-advisory
- https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9cexploit, mitigation, vendor-advisory
- https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5wvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.