CVE-2026-2880 json
@fastify/middie has an improper path normalization vulnerability
published 8mo ago modified 4mo ago also GHSA-8p85-9qpw-fwgw , EUVD-2026-9049
- cvss
- 9.1
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 37%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- npm @fastify/middie 9.2.0
- @fastify/middie @fastify/middie 9.2.0
Is CVE-2026-2880 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 8mo ago
Exploit prediction
0.43% chance of exploitation in the next 30 days, higher than 37% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 8.2 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N |
| CNA | 4.0 | 8.2 | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD | 3.1 | 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| npm | @fastify/middie | <9.2.0 |
9.2.0 |
Affected products
- @fastify/middie @fastify/middie
Classification
- Weakness
-
- CWE-20 Improper Input Validation
References
-
github.com
/fastify/middie/commit/140e0dd0359d890fec7e6ea1dcc5134d6bd554d4
web
-
github.com
/fastify/middie/security/advisories/GHSA-8p85-9qpw-fwgw
web, mitigation, vendor-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-2880
advisory
-
fluidattacks.com
/advisories/jimenez
web
-
fluidattacks.com
/advisories/policy
web
-
github.com
/fastify/middie
package
-
github.com
/fastify/middie/releases/tag/v9.2.0
web
Sources
- CVE List CVE-2026-2880
- GitHub Advisory GHSA-8p85-9qpw-fwgw
- NVD CVE-2026-2880
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