CVE-2026-8139

Medium

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.

SeverityMedium

CVSS5.4

Exploit probability—

Product

Concretecms Concrete Cms

PublishedMay 21, 2026

First seenMay 21, 2026

Weakness typeCWE-79Cross-site scripting (XSS)

How to fix

Update

concrete5/concrete59.5.1 or later

Vendor advisories

documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes

Affected products

Product	Affected versions	Fixed in
concretecms concrete_cms	v ≤ 9.5.0	—
concrete5/concrete5Packagist	v < 9.5.1	9.5.1

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