Answer in brief
CVE-2026-85386 records a High severity (CVSS 7.3) vulnerability in Concrete CMS before 9.5.4 stored is vulneratble to cross-site scripting via unauthenticated XML/XSLT file upload in the Form Block. The current sources do not mark it as known exploited. The current feed maps Concrete CMS/Concrete CMS (generic), Concrete CMS/Concrete CMS (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Concrete CMS/Concrete CMS (generic), Concrete CMS/Concrete CMS (generic). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Concrete CMS/Concrete CMSgeneric | 5.0.0 | Not reported |
| Concrete CMS/Concrete CMSgeneric | >=5.0.0 <=9.5.3 | Not reported |
Published upstream
Sep 16, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 21, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 16, 2026
Concrete CMS before 9.5.4 did not sanitize XML and XSLT documents uploaded through a public Form Block file-upload question. Plain XML uploads were validated by file extension only and stored as publicly accessible files that were served inline from the application's own origin. An unauthenticated visitor could therefore store an XML document containing an xml-stylesheet processing instruction that referenced an attacker-supplied, same-origin XSLT stylesheet. When a victim opened the stored file directly in a browser, the browser fetched the stylesheet, transformed the document into HTML, and executed attacker-controlled JavaScript in the Concrete CMS origin (stored cross-site scripting). If the victim was an authenticated administrator, the script could act with that administrator's session, and the reporter demonstrated creation of a new user in the Administrators group. 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:L/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Valentin SARRE (Independent security researcher) for reporting.
Quoted source text, attributed separately from HOL analysis.