CVE-2026-8426

HIGH EPSS 6.7%
Published May 21, 20261mo ago · Modified Jun 17, 20262w ago
7.5 CVSS 4.0
High
Find Similar
Published May 21, 2026 1mo ago
Last Modified Jun 17, 2026 2w ago

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.

CVSS Details

Base Score
7.5
Exploitability
Impact
Vector string
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
Attack Vector Network
Attack Complexity High
Privileges Required None
User Interaction A
Scope X

Threat Intelligence

EPSS Exploit Probability
6.7% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 2

CWE-352 Cross-Site Request Forgery (CSRF) Authentication
CWE-829

Affected Products 1

VendorProductVersionRange
concretecmsconcrete_cms* <9.5.1

References 1

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.