How severe is CVE-2026-87028?

CVE-2026-87028 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-87028 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (29th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-87028?

CVE-2026-87028 affects Concretecms Concrete Cms. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-87028?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-87028 published?

CVE-2026-87028 was published on 2026-09-16 and last updated on 2026-09-21.

CVE-2026-87028

CVE-2026-87028 is a medium-severity vulnerability in Concretecms Concrete Cms with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-862.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 5.3
EPSS exploit prediction: 0% (29th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-862
Affected product: Concretecms Concrete Cms
Published: 2026-09-16
Last modified: 2026-09-21

Description

Concrete CMS 9 through 9.5.3 did not confirm that a board InstanceItem submitted to the custom-slot preview endpoint belonged to the board instance the requesting user was authorized to edit, and did not enforce page-view permission before generating page-backed summary content. As a result, an authenticated user holding edit-board-contents permission on a single board instance could submit the identifier of an item belonging to a different board instance and receive summary fields, including the page title and description, of an underlying page the same user was otherwise forbidden to view. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.3 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Pakung for reporting.

Frequently asked questions

What is CVE-2026-87028?: Concrete CMS 9 through 9.5.3 did not confirm that a board InstanceItem submitted to the custom-slot preview endpoint belonged to the board instance the requesting user was authorized to edit, and did not enforce page-view permission before generating page-backed summary content. As a result, an authenticated user holding edit-board-contents permission on a single board instance could submit the identifier of an item belonging to a different board instance and receive summary fields, including the page title and description, of an underlying page the same user was otherwise forbidden to view. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.3 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Pakung for reporting.
How severe is CVE-2026-87028?: CVE-2026-87028 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-87028 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (29th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-87028?: CVE-2026-87028 affects Concretecms Concrete Cms. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-87028?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-87028 published?: CVE-2026-87028 was published on 2026-09-16 and last updated on 2026-09-21.

References

https://documentation.concretecms.org/developers/introduction/version-history/954-release-notes

Affected products (1)

cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*

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