CVE-2026-18117 — Concrete CMS 9.0.0 to 9.5.2 is vulnerable to Stored XSS in Custom Page Alias Name

Concrete CMS 9.0.0 through 9.5.3 is vulnerable to stored XSS via the custom page alias name (customAliasName) because the Edit Alias dialog applied only trim() to the submitted value and performed no input neutralization. An authenticated user holding canWrite (editor) permission on a page could store a malicious alias name that was later rendered unescaped in the administrative Sitemap panel, where it executed automatically in any administrator or editor session that opened the panel, allowing an editor to escalate to administrator through the victim's active session. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N. Thanks Nguyen Manh Thuan for reporting.

Published Sep 14, 2026Updated Sep 14, 2026Sources: cvelistV5, ConcreteCMS

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

Not scored

FIRST has not published a score

Affects

concrete cms

concrete_cms

CVSS base

7.3

HIGH

Affected scope

The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.

Vendors (1)

concrete cms

Products (1)

concrete cms

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
7.3	CVSS 4.0	HIGH	—	—	cvelistV5

Weakness & attack patterns

CWE-79

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Search application, proxy, and WAF logs for requests touching /AV:N/AC:L/AT:P/PR:H/UI:P/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N.

References

1 on the record

documentation.concretecms.org/developers/introduction/version-history/953-release-notes
release-notes

Elsewhere on this site

concrete cmsevery CVE for this vendor
CWE-79other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.