EUVD-2026-75885
GHSA-cwc3-87mf-4ggw
Severity by source
CVSS:4.0/AV:N/AC:L/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
Network-reachable unauthenticated endpoint; impact is limited to partial confidentiality (event metadata only); no integrity or availability impact.
Primary rating from Vendor (ConcreteCMS).
CVSS VectorVendor: ConcreteCMS
Lifecycle Timeline
2DescriptionCVE.org
Concrete CMS 9.5.2 and below is vulnerable to an authorization bypass (IDOR) because the frontend calendar lightbox endpoint (/ccm/calendar/view_event/{bID}/{occurrence_id}) does not verify that the caller is permitted to view the calendar that owns the requested event occurrence. The controller loads the occurrence directly from an attacker‑supplied, sequential identifier without confirming that it belongs to the calendar configured on the referenced block. An unauthenticated visitor who can render any public calendar block with lightbox properties enabled could therefore supply an arbitrary occurrence identifier and disclose event metadata - title, date, description, page link, and configured event attributes - from calendars they are not permitted to view. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks riodrwn for reporting.
AnalysisAI
Unauthenticated event metadata disclosure in Concrete CMS 9.5.2 and earlier allows any visitor to enumerate private calendar event details via a sequential IDOR on the frontend lightbox endpoint. The controller at /ccm/calendar/view_event/{bID}/{occurrence_id} loads occurrence records directly from attacker-supplied integer IDs without verifying that the occurrence belongs to the calendar block referenced by bID or that the caller holds read permission on the owning calendar. …
Unlock full vulnerability intelligence
- Risk assessment & exploitation conditions
- Attack chain visualization
- Remediation with exact patch versions
- Threat intelligence from 22 sources
- Personal watchlist & email alerts
Free forever · No credit card required
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the target Concrete CMS installation running version 9.5.2 or earlier has at least one public-facing page with a calendar block that has lightbox properties enabled and is accessible without authentication. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The Concrete CMS security team assigned a CVSS 4.0 score of 6.3 with vector AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N, which accurately reflects the exposure. … 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 to Concrete CMS 9.5.3, which addresses this authorization bypass per vendor release notes at https://documentation.concretecms.org/developers/introduction/version-history/953-release-notes. … Detailed patch versions, workarounds, and compensating controls in full report. |
Threat intelligence, references, and detailed analysis are available after sign-in.
More in Concrete Cms
View allA bypass of adding remote files in Concrete CMS (previously concrete5) File Manager leads to remote code execution in Co
Concrete5 through 8.5.5 deserializes Untrusted Data. Rated high severity (CVSS 7.2), this vulnerability is remotely expl
Concrete5 up to and including 8.5.2 allows Unrestricted Upload of File with Dangerous Type such as a .php file via File
Concrete5 before 8.5.3 allows Unrestricted Upload of File with Dangerous Type such as a .phar file. Rated high severity
A Server Side Request Forgery (SSRF) vulnerability in tools/files/importers/remote.php in concrete5 8.2.0 can lead to at
Unauthenticated file usage disclosure in Concrete CMS 9.5.0 and below exposes internal page structure to any network-acc
concrete5 8.1.0 places incorrect trust in the HTTP Host header during caching, if the administrator did not define a "ca
Concrete CMS versions below 9.4.8 contain a cross-site request forgery vulnerability in the Anti-Spam Allowlist Group Co
concrete5 8.1.0 has CSRF in Thumbnail Editor in the File Manager, which allows remote attackers to disable the entire in
Unauthenticated information disclosure in Concrete CMS 9.5.0 and earlier allows remote attackers to enumerate all conver
Unauthenticated information disclosure in Concrete CMS 9.5.0 and below allows any network-accessible attacker to enumera
Concrete CMS before 8.5.13 and 9.x before 9.2.2 allows unauthorized access because directories can be created with insec
Same weakness CWE-862 – Missing Authorization
View allShare
External POC / Exploit Code
Leaving vuln.today