CVE-2026-81927: low-severity vulnerability in Concrete CMS
Concrete CMS before 9.5.3 is vulnerable to Stored XSS via SVG upload in "Reject" sanitization mode
Published · Updated
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8Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 1.8epss 0.2%
Concrete CMS before 9.5.3 contained a stored cross-site scripting vulnerability in SVG file handling. When SVG processing was set to the non-default "Reject files containing potentially harmful elements" mode (concrete.file_manager.images.svg_sanitization.action = reject), uploaded SVGs were checked only against a small built-in blocklist covering the script element and on* event-handler attributes; the broader enshrined/svg-sanitize pass still ran, but its result was discarded, so vectors it would have stripped, such as a javascript: URI in an xlink:href, were stored unmodified and executed when the file was opened directly. A user able to upload files could thereby run arbitrary JavaScript in the browser of any user who viewed the file. The default sanitize mode was not affected. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 1.8 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Oriol Ortiz for reporting.
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Affected products
Concrete CMS · Concrete CMSRelated CVEs — Concrete CMS
In the same product, most dangerous first.
CVE-2026-18110HIGHConcrete CMS 9.0.0 through 9.5.2 is vulnerable to missing authorization in the user selector autocomplete endpoint (/ccm/system/user/autocomplete), allowing an unauthenticated attacker to retrieve the complete backend user directory — internal ID, usernameEPSS 1.6%CVE-2026-6826MEDIUMConcrete 9.5.0 and below has file usage disclosure via missing permission check in Usage controllerEPSS 1.5%CVE-2024-1247LOWConcrete CMS version 9 before 9.2.5 vulnerable to stored XSS via the Role Name fieldEPSS 1.2%CVE-2026-8134CRITICALConcrete CMS 9.5.0 and below is vulnerable to Authenticated RCE via Composer customTemplate Path Traversal leading to PHP File InclusionEPSS 0.7%CVE-2026-3452HIGHConcrete CMS below 9.4.8 is vulnerable to stored deserialization leading to RCE in the Express Entry List block.EPSS 0.7%CVE-2011-3183—CVE-2011-3183EPSS 0.7%