> CVE-2026-8426 [HIGH]

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PUBLISHED
2026-05-21 21:16
MODIFIED
2026-05-21 21:16
CVSS_SCORE V3
7.5
EPSS (Prob. Exploit)
0.17%
Top 93.6%
DATA SOURCES:
NVD đź”— 2026-05-21 CWE MITRE đź”— 2026-11-01 FIRST EPSS đź”— 2026-11-01 GITHUB đź”— 2026-10-29 OSV đź”— 2026-11-02

> DESCRIPTION

Concrete CMS 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>. An attacker who controls the remote package returned for a known marketplace item ID can overwrite the package PHP on disk and force its upgrade() method to execute in a single browser navigation. This results in remote code execution as the web server user.   In order to be vulnerable, the victim must be passing canInstallPackages, victim site must be connected to the Concrete marketplace; and the attacker controls the package returned for a marketplace item ID already installed on the victim site. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 7.5 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks https://github.com/maru1009 for reporting.

> 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:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/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

> MÉTRIQUES CVSS DÉTAILLÉES

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/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
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
High (H)
Conditions spécifiques doivent être réunies pour exploiter
PR (Privilèges Requis)
Privileges Required
None (N)
Aucune authentification requise
UI (Interaction Utilisateur)
User Interaction
Required (R)
Nécessite une action utilisateur (clic lien, ouverture fichier, etc.)
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
High (H)
Interruption totale du service possible

> RÉSUMÉ DES IMPACTS

Confidentialité
High
Divulgation totale d'informations
Intégrité
High
Modification totale des données possible
Disponibilité
High
Interruption totale du service possible

> WEAKNESSES

CWE-352 CWE-829

> CWE DETAILED DESCRIPTIONS

CWE-352: Cross-Site Request Forgery - The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor. | CWE-829: Inclusion of Functionality from Untrusted Control Sphere - The product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere.

> GITHUB SECURITY ADVISORY

GHSA-5rj5-gfmr-hrc3 HIGH

Concrete CMS does not validate a CSRF token before processing requests to `/dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>`

AFFECTED PACKAGES:
COMPOSER / concrete5/concrete5
< 9.5.1
Fixed in: 9.5.1

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

Concrete CMS 9.5.0 and below is vulnerable to CSRF on prepare_remote_upgrade() leading to one-request RCE via package overwrite

AFFECTED PACKAGES:
Unknown / Unknown
38 versions affected
ALIASES:
GHSA-5rj5-gfmr-hrc3

> HISTORIQUE DES MODIFICATIONS

Première apparition
21/05/2026 21:16
Source: NVD
📊 ENRICHISSEMENT 01/11/2026 06:59
CWE
Champ modifié: Description CWE
Ancienne valeur:
CWE-352: Cross-Site Request Forgery (CSRF) - The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could hav...
Nouvelle valeur:
CWE-352: Cross-Site Request Forgery - The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have origi...
📊 ENRICHISSEMENT 01/06/2026 06:01
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-352: Cross-Site Request Forgery (CSRF) - The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could hav...
Total des modifications: 2 Dernière mise à jour: 6 days ago

> REFERENCES

https://documentation.concretecms.org/9-x/developers/introduction/version-histor...
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