Is CVE-2026-8340 in the CISA KEV catalog?

No. CVE-2026-8340 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-8340?

CVE-2026-8340 has a CVSS v3 base score of 4.3 (MEDIUM).

What is the EPSS score for CVE-2026-8340?

CVE-2026-8340 has an EPSS score of 0.10% (1th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-8340?

Upgrade concrete cms to 9.5.1 or later.

CVE & CISA-KEV Catalog

CVE-2026-8340

MEDIUM

4.3

CVSS v3

NVD

Description

Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion. Victim with edit_file_contents permission is CSRF'd into publishing an attacker-chosen previously-uploaded version (downgrade to an older version of a file, or activation of a co-editor's unpublished version). The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.

CWE-352Cross-Site Request Forgery

How to fix

Remediation Available

concrete cmsNVD

Affected:< 9.5.1Fixed in:9.5.1CVE-2026-8340derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Exploit Intelligence

0.10%probability of exploitation in 30 days

1stpercentile

Low risk: more likely to be exploited than 1% of all known CVEs.

References

Release Notes1

documentation.concretecms.org

Related Vulnerabilities

Other CWE-352 (Cross-Site Request Forgery) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2016-6277	High	8.8	100%	KEV	-
CVE-2014-0054	Medium	6.8	91%	-	Fix
CVE-2013-6429	Medium	6.8	90%	-	Fix
CVE-2022-41622	High	8.8	88%	-	-
CVE-2018-7700	High	8.8	75%	-	-
CVE-2015-2295	Medium	6.8	66%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-26.