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Concrete CMS CVE-2026-18120

| EUVDEUVD-2026-80894 MEDIUM
Missing Authorization (CWE-862)
2026-09-16 ConcreteCMS GHSA-3w9f-9wfp-x8gr
6.3
CVSS 4.0 · Vendor: ConcreteCMS
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Severity by source

Vendor (ConcreteCMS) PRIMARY
6.3 MEDIUM
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
3.7 LOW

Unauthenticated network endpoint (AV:N/PR:N) but attacker must first obtain a valid entity identifier (AC:H); read-only partial disclosure gives C:L with no integrity or availability impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (ConcreteCMS).

CVSS VectorVendor: ConcreteCMS

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

1
Analysis Generated
Sep 16, 2026 - 17:45 vuln.today

DescriptionCVE.org

Concrete CMS before 9.5.3 exposed a legacy Express entry search endpoint that returned entry result JSON without invoking the canViewExpressEntries() permission check applied by the normal dashboard and CSV Export flow. An unauthenticated visitor who knew or discovered an Express entity identifier could enumerate that entity's entry search results, disclosing attribute values intended to be restricted to privileged users. For Express entities that do not support entry-specific permissions (i.e., supportsEntrySpecificPermissions() returns false), per-entry permission filtering is additionally disabled via EntryList::ignorePermissions(). The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Daniel Powell for reporting.

AnalysisAI

Unauthenticated information disclosure in Concrete CMS releases before 9.5.3 allows a remote visitor who knows or can guess a valid Express entity identifier to query a legacy Express entry search endpoint that omits the canViewExpressEntries() permission check, returning entry attribute values that should be restricted to privileged users. The impact is read-only (C:L/I:N/A:N) and exploitation requires that identifier prerequisite, which is why the vendor and independent assessments both score it as hardening-limited rather than trivially exploitable; disclosure is worse for Express entities where supportsEntrySpecificPermissions() returns false, because EntryList::ignorePermissions() then bypasses per-entry filtering entirely. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires a Concrete CMS instance older than 9.5.3 that exposes the legacy Express entry search endpoint, and the attacker must first know or discover a valid Express entity identifier - this identifier prerequisite is the core limiting factor (reflected as AC:H/AT:P). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a genuine but low-priority issue. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade Concrete CMS to version 9.5.3 or later, which restores the canViewExpressEntries() authorization check on the Express entry search path and stops the permission-bypassing EntryList::ignorePermissions() behavior for entities lacking entry-specific permissions; see the vendor release notes at https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes for the patch summary. … Detailed patch versions, workarounds, and compensating controls in full report.

Threat intelligence, references, and detailed analysis are available after sign-in.

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CVE-2026-18120 vulnerability details – vuln.today

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