Instituto Nacional de ciberseguridad. Sección Incibe
Instituto Nacional de Ciberseguridad. Sección INCIBE-CERT

Go to Calendar     Go to Press Room     Go to Newsletters subscription

Search

CVE-2026-8134

Severity CVSS v4.0:
CRITICAL
Type:
CWE-23 Relative Path Traversal
Publication date:
21/05/2026
Last modified:
26/05/2026

Description

Concrete CMS 9.5.0 and below fails to sanitize path traversal sequences in the ptComposerFormLayoutSetControlCustomTemplate field when saving page type composer form layouts. An authenticated rogue administrator with composer form editing rights can exploit this to include arbitrary readable files on the server. Combined with the file uploader's extension-only validation (which permits PHP code in files saved with image extensions like .png), this can result in authenticated remote code execution. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 9.4 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H   Thanks Yonatan Drori (Tenzai) for reporting.

Impact

Vector 4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H CVSS v4.0 Severity and Metrics:

Base Score: 9.40 CRITICAL
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Attack Vector (AV): Network
Attack Complexity (AC): Low
Attack Requirements (AT): None
Privileges Required (PR): High
User Interaction (UI): None
Confidentiality (VC): High
Integrity (VI): High
Availability (VA): High
Confidentiality (SC): High
Integrity (SI): High
Availability (SA): High

Base Score 4.0
9.40
Severity 4.0
CRITICAL
Vector 3.x
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H CVSS v3.1 Severity and Metrics:

Base Score: 7.20 HIGH
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): High
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): High
Integrity (I): High
Availability (A): High

Base Score 3.x
7.20
Severity 3.x
HIGH

Vulnerable products and versions

CPE From Up to
cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:* 9.5.0 (including)

To consult the complete list of CPE names with products and versions, see this page


References to Advisories, Solutions, and Tools