EUVD-2026-78839
GHSA-vgg6-gg65-r39p
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V6 - Authentication Authentication required for critical functions
MITRE ATT&CK
1 technique across 1 tactic: Initial Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
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Alert meAnalysisAIv1 – Sep 15, 2026
Stored cross-site scripting in Concrete CMS lets any user holding page-editing permissions — for example Add Block combined with Edit Contents on a single page — plant a crafted external link value in Feature, Feature Link, Hero Image, or Image blocks that breaks out of the link markup and injects JavaScript. Because the payload is persisted and rendered without output escaping, the script executes in the browser session of every user who later views, previews, or edits that page, enabling session hijacking and privilege escalation up to full administrative takeover. The vendor scored this 8.5 (CVSS v4.0, PR:H/UI:P); no public exploit code or CISA KEV entry was provided at time of analysis, so exploitation is currently a realistic internal-threat and low-privileged-editor risk rather than a confirmed internet-wide campaign.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Primary rating from Vendor (ConcreteCMS) · only source for this CVE.
CVSS VectorVendor: ConcreteCMS
DescriptionCVE.org
Concrete CMS 9 before 9.5.3 was vulnerable to stored cross-site scripting (XSS) in the Feature, Feature Link, Hero Image, and Image blocks and before Concrete 8.5.21 in the feature and Image blocks because the external link URL was insufficiently validated by the link filter and was rendered without output escaping. A user with page-editing permissions (such as Add Block combined with Edit Contents on a single page) could store a crafted external link value that broke out of the link markup and injected arbitrary JavaScript. The script executed in the browser session of any user who subsequently viewed, previewed, or edited the affected page, which could lead to session hijacking and escalation of privileges up to full administrative takeover. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 8.5 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks to KhanMarshai for reporting this issue.
Threat Intelligence Overview
NVD
CVE.org
EPSS
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
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