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CVE-2026-81903

Concrete CMS 9.0.0 to 9.5.2 is vulnerable to Stored XSS via Page Container icon

CVSS 4.0 7.0 HIGHCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-81903

Published

Concrete CMS versions 9.0.0 to 9.5.2 stored the Page Container icon value submitted through the dashboard without validating it against the set of known container icons. The unvalidated value was later concatenated into the src attribute of an img tag by a helper that did not encode attribute output, and was rendered raw in the Containers dashboard list and editor views. A user with delegated access to the Page Containers dashboard could store a crafted icon value that broke out of the src attribute and executed script in the authenticated session of another editor or administrator who viewed the list, enabling session token theft and privileged dashboard actions. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.0 with vector CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Andrew Gonzalez for reporting.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-81903

Published

Concrete CMS

https://github.com/concretecms/concretecms

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "Concrete CMS",
                    "product": "Concrete CMS",
                    "collectionURL": "https://github.com/concretecms/concretecms",
                    "repo": "https://github.com/concretecms/concretecms",
                    "versions": [
                        {
                            "status": "affected",
                            "version": "9.0.0",
                            "lessThanOrEqual": "9.5.2",
                            "versionType": "git"
                        }
                    ],
                    "defaultStatus": "unaffected"
                }

Original source record · Cite this exact observation · Complete original publisher JSON