V
Scaner-VS
HomeCatalogSourcesCWECAPECATT&CKMitigationsProductsVendorsDocs
CVE-2026-33808
CVE
Critical

Impact@fastify/express v4.0.4 and earlier fails to normalize URLs before passing them to Express middleware when Fastify router normalizati…

CVSS
9.1
Critical
EPSS
0.00
p37
Published
2026-01-01
Updated
2026-01-01
Description

Impact@fastify/express v4.0.4 and earlier fails to normalize URLs before passing them to Express middleware when Fastify router normalization options are enabled. This allows complete bypass of path-scoped authentication middleware via duplicate slashes when ignoreDuplicateSlashes is enabled, or via semicolon delimiters when useSemicolonDelimiter is enabled. In both cases, Fastify router normalizes the URL and matches the route, but @fastify/express passes the original un-normalized URL to Express middleware, which fails to match and is skipped. An unauthenticated attacker can access protected routes by manipulating the URL path. PatchesUpgrade to @fastify/express v4.0.5 or later.

Tags · CWE
Pre-auth
CWE-436
CAPEC-34
CAPEC-105
CAPEC-273
Affected products
Fastify\/express < 4.0.5
CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/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
Timeline
2026-01-01
Published
2026-01-01
Updated
CVSS 3.1 breakdown
Attack Vector
AV: N
Network (N)
Attack Complexity
AC: L
Low (L)
Attack Requirements
AT: P
Present
Privileges Required
PR: N
None (N)
User Interaction
UI: N
None (N)
Vulnerable System Confidentiality
VC: H
High (H)
Vulnerable System Integrity
VI: H
High (H)
Vulnerable System Availability
VA: N
None (N)
Subsequent System Confidentiality
SC: N
None (N)
Subsequent System Integrity
SI: N
None (N)
Subsequent System Availability
SA: N
None (N)
Exploit Code Maturity
E: X
Not Defined
Confidentiality Requirement
CR: X
Not Defined
Integrity Requirement
IR: X
Not Defined
Availability Requirement
AR: X
Not Defined
Modified Attack Vector
MAV: X
Not Defined
Modified Attack Complexity
MAC: X
Not Defined
Modified Attack Requirements
MAT: X
Not Defined
Modified Privileges Required
MPR: X
Not Defined
Modified User Interaction
MUI: X
Not Defined
Modified Vulnerable System Confidentiality
MVC: X
Not Defined
Modified Vulnerable System Integrity
MVI: X
Not Defined
Modified Vulnerable System Availability
MVA: X
Not Defined
Modified Subsequent System Confidentiality
MSC: X
Not Defined
Modified Subsequent System Integrity
MSI: X
Not Defined
Modified Subsequent System Availability
MSA: X
Not Defined
s
S: X
X
au
AU: X
X
r
R: X
X
v
V: X
X
re
RE: X
X
u
U: X
X
Exploit indicators
EPSS
0.005 · p37
Known exploited (KEV)
No
Known exploits — Сканер-ВС
No Сканер-ВС checks registered for this vulnerability yet.
Affected products
ProductVendorStatus
fastify/express*Tracked