Critical severity9.1NVD Advisory· Published Feb 27, 2026· Updated May 14, 2026
CVE-2026-2880
CVE-2026-2880
Description
A vulnerability in @fastify/middie versions < 9.2.0 can result in authentication/authorization bypass when using path-scoped middleware (for example, app.use('/secret', auth)).
When Fastify router normalization options are enabled (such as ignoreDuplicateSlashes, useSemicolonDelimiter, and related trailing-slash behavior), crafted request paths may bypass middleware checks while still being routed to protected handlers.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
@fastify/middienpm | < 9.2.0 | 9.2.0 |
Affected products
3- @fastify/middie/@fastify/middiev5Range: 0.0.0
Patches
Vulnerability mechanics
References
7- github.com/advisories/GHSA-8p85-9qpw-fwgwghsaADVISORY
- github.com/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgwnvdMitigationVendor AdvisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-2880ghsaADVISORY
- fluidattacks.com/advisories/jimenezghsaWEB
- fluidattacks.com/advisories/policyghsaWEB
- github.com/fastify/middie/commit/140e0dd0359d890fec7e6ea1dcc5134d6bd554d4ghsaWEB
- github.com/fastify/middie/releases/tag/v9.2.0ghsaWEB
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