CVE-2026-112362 @fastify/express - Broken Access Control

@fastify/express 4.0.5 through 4.0.8 contains a broken access control caused by mismatch in path normalization between Fastify router and Express middleware when ignoreDuplicateSlashes option is enabled, letting unauthenticated attackers bypass authentication middleware on scoped routes, exploit requires ignoreDuplicateSlashes option enabled.

CVSS base score 9.1 /10
Critical
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.36% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Broken Access Control
Impact
Broken Access Control
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
27 October 2026
Updated
29 October 2026
Weakness
CWE-436

Vendor fix

Upgrade to version 4.0.9 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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