> CVE-2025-62800 [MEDIUM]

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PUBLISHED
2025-10-28 22:15
MODIFIED
2025-10-28 22:15
CVSS_SCORE V3
5.3
EPSS (Prob. Exploit)
0.28%
Top 79.8%
DATA SOURCES:
NVD 🔗 2025-10-28 CVE PROJECT 🔗 2026-01-19 CWE MITRE 🔗 2026-11-01 FIRST EPSS 🔗 2026-11-08 GITHUB 🔗 2026-10-28 OSV 🔗 2026-11-08

> DESCRIPTION

FastMCP is the standard framework for building MCP applications. Versions prior to 2.13.0 have a reflected cross-site scripting vulnerability in the OAuth client callback page (oauth_callback.py) where unescaped user-controlled values are inserted into the generated HTML, allowing arbitrary JavaScript execution in the callback server origin. The issue is fixed in version 2.13.0.

> AFFECTED_PRODUCTS

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

> CVSS V3 METRICS

CVSS_VECTOR
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/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

> MÉTRIQUES CVSS DÉTAILLÉES

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/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
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
Unknown (P)
Interaction inconnue
S (Périmètre)
Scope
Unchanged (U)
Impact reste dans le périmètre du composant compromis
C (Impact Confidentialité)
Confidentiality Impact
None (N)
Aucune divulgation d'informations
I (Impact Intégrité)
Integrity Impact
None (N)
Aucune modification de données possible
A (Impact Disponibilité)
Availability Impact
None (N)
Aucune interruption de service

> RÉSUMÉ DES IMPACTS

Confidentialité
None
Aucune divulgation d'informations
Intégrité
None
Aucune modification de données possible
Disponibilité
None
Aucune interruption de service

> WEAKNESSES

CWE-79

> CWE DETAILED DESCRIPTIONS

CWE-79: Improper Neutralization of Input During Web Page Generation - The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

> GITHUB SECURITY ADVISORY

GHSA-mxxr-jv3v-6pgc MODERATE

FastMCP vulnerable to reflected XSS in client's callback page

AFFECTED PACKAGES:
PIP / fastmcp
< 2.13.0
Fixed in: 2.13.0

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

FastMCP vulnerable to reflected XSS in client's callback page

AFFECTED PACKAGES:
Unknown / Unknown
67 versions affected
ALIASES:
GHSA-mxxr-jv3v-6pgc, PYSEC-2026-1364

> HISTORIQUE DES MODIFICATIONS

Première apparition
28/10/2025 22:15
Source: NVD
📊 ENRICHISSEMENT 01/11/2026 06:58
CWE
Champ modifié: Description CWE
Ancienne valeur:
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') - The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in...
Nouvelle valeur:
CWE-79: Improper Neutralization of Input During Web Page Generation - The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a...
📊 ENRICHISSEMENT 19/01/2026 17:36
CVEPROJECT
Champ modifié: CVE Project
Ancienne valeur:
Non
Nouvelle valeur:
Oui
📊 ENRICHISSEMENT 01/11/2025 06:01
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') - The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in...
Total des modifications: 3 Dernière mise à jour: 1 week ago

> REFERENCES

https://github.com/jlowin/fastmcp/security/advisories/GHSA-mxxr-jv3v-6pgc
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