ConcreteCMS Cross-site Scripting vulnerability

published 2023-10-06 3 y ago modified 2026-09-10 1 mo ago also GHSA-437p-jfm4-2387 , EUVD-2023-2636

cvss: 4.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.6%; EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits: 0; none known

A Cross Site Scripting (XSS) vulnerability in Concrete CMS v.9.2.1 allows an attacker to execute arbitrary code via a crafted script to the SEO - Extra from Page Settings. NOTE: the vendor disputes this because this SEO-related header change can only be made by an admin, and allowing an admin to place JavaScript there is an intentional customization feature.

Exploit prediction

0.60% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/sromanhu/ConcreteCMS-Stored-XSS---SEO referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	4.8	CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
GitHub	3.1	5.4	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
packagist	concrete5/concrete5	<=9.2.1	no fix listed

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

github.com /sromanhu/ConcreteCMS-Stored-XSS---SEO
web, exploit
concretecms.org /about/project-news/security/security-advisory-2023-10-31-concrete-cms-rejects-cve-2023-44760-and-cve-2023-447
web, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2023-44766
advisory
github.com /concretecms/concretecms
web

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary