> CVE-2026-33807 [CRITICAL]

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PUBLISHED
2026-04-15 10:16
MODIFIED
2026-04-15 14:16
CVSS_SCORE V3
9.1
EPSS (Prob. Exploit)
0.53%
Top 55.7%
DATA SOURCES:
NVD đź”— 2026-04-15 CWE MITRE đź”— 2026-11-01 FIRST EPSS đź”— 2026-10-25 GITHUB đź”— 2026-11-05

> DESCRIPTION

@fastify/express v4.0.4 and earlier contains a path handling bug in the onRegister function that causes middleware paths to be doubled when inherited by child plugins. When a child plugin is registered with a prefix that matches a middleware path, the middleware path is prefixed a second time, causing it to never match incoming requests. This results in complete bypass of Express middleware security controls, including authentication, authorization, and rate limiting, for all routes defined within affected child plugin scopes. No special configuration or request crafting is required. Upgrade to @fastify/express v4.0.5 or later.

> AFFECTED_PRODUCTS

ℹ️ Aucun produit affecté n'a encore été publié par NVD pour cette CVE.

> CVSS V3 METRICS

CVSS_VECTOR
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EXPLOITABILITY
3.9
IMPACT
5.2

> MÉTRIQUES CVSS DÉTAILLÉES

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Métrique Valeur Interprétation
AV (Vecteur d'Attaque)
Attack Vector
Network (N)
Exploit possible à distance via réseau (HTTP, API, etc.)
AC (Complexité d'Attaque)
Attack Complexity
Low (L)
Peu de conditions requises pour exploiter
PR (Privilèges Requis)
Privileges Required
None (N)
Aucune authentification requise
UI (Interaction Utilisateur)
User Interaction
None (N)
Aucune interaction utilisateur nécessaire
S (Périmètre)
Scope
Unchanged (U)
Impact reste dans le périmètre du composant compromis
C (Impact Confidentialité)
Confidentiality Impact
High (H)
Divulgation totale d'informations
I (Impact Intégrité)
Integrity Impact
High (H)
Modification totale des données possible
A (Impact Disponibilité)
Availability Impact
None (N)
Aucune interruption de service

> RÉSUMÉ DES IMPACTS

Confidentialité
High
Divulgation totale d'informations
Intégrité
High
Modification totale des données possible
Disponibilité
None
Aucune interruption de service

> WEAKNESSES

CWE-436

> CWE DETAILED DESCRIPTIONS

CWE-436: Interpretation Conflict - Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state.

> GITHUB SECURITY ADVISORY

GHSA-hrwm-hgmj-7p9c CRITICAL

@fastify/express's middleware path doubling causes authentication bypass in child plugin scopes

AFFECTED PACKAGES:
NPM / @fastify/express
<= 4.0.4
Fixed in: 4.0.5

> HISTORIQUE DES MODIFICATIONS

Première apparition
15/04/2026 10:16
Source: NVD
📊 ENRICHISSEMENT 01/05/2026 06:01
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-436: Interpretation Conflict - Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state.
Total des modifications: 1 Dernière mise à jour: 6 months ago

> REFERENCES

https://cna.openjsf.org/security-advisories.html
https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p...
https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p...
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