Vulnerability · Published May 21, 2026 · Assigned by ConcreteCMS

CVE-2026-8139Concrete CMS 9.5.0 and below is vulnerable to Stored XSS via external-link page cvName

Low 2.0

In plain English

A low-severity cross-site scripting in Concrete CMS from Concrete CMS. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)2.0Low

Exploit odds (30 days)0.1%top 95.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Packagist	concrete5/concrete5	9.5.1	GHSA-pcrh-gj77-j4mw

Affected products (as reported)

Vendor	Product	Versions
Concrete CMS	Concrete CMS	5.0 – through 9.5.0

Weakness: CWE-79 · 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

References

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