Stored XSS in Concrete CMS via External-Link Page

Publication date: 2026-05-21

Last updated on: 2026-05-26

Assigner: ConcreteCMS

Description

Concrete CMS 9.5.0 and below is vulnerable to Stored XSS via external-link page cvName because updateCollectionAliasExternal bypasses being sanitized. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.0 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori (Tenzai) for reporting.

CVSS Scores

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Meta Information

Published

2026-05-21

Last Modified

2026-05-26

Generated

2026-07-02

AI Q&A

2026-05-22

EPSS Evaluated

2026-06-30

NVD

CVE-2026-8139

EUVD

EUVD-2026-31380

Affected Vendors & Products

Vendor	Product	Version / Range
concretecms	concrete_cms	to 9.5.0 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-79	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.

Attack-Flow Graph

Executive Summary

This vulnerability affects Concrete CMS version 9.5.0 and below. It is a Stored Cross-Site Scripting (XSS) issue that occurs via the external-link page parameter named cvName. The problem arises because the function updateCollectionAliasExternal does not properly sanitize input, allowing malicious scripts to be stored and later executed in users' browsers.

Impact Analysis

The vulnerability can allow attackers to inject malicious scripts into the website that will be stored and executed when other users visit the affected pages. This can lead to unauthorized actions performed on behalf of users, theft of sensitive information, or other malicious activities. However, the CVSS score of 2.0 indicates a relatively low severity, suggesting limited impact under certain conditions.

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