How severe is CVE-2026-8237?

No CVSS score has been assigned to CVE-2026-8237 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-8237?

CVE-2026-8237 affects the following packages: concrete5/concrete5 (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-8237?

Update concrete5/concrete5 to 9.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-8237 is resolved across your whole dependency graph.

How do I detect CVE-2026-8237 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for concrete5/concrete5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-8237 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2026-8237 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-8237 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-8237?

CVE-2026-8237 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 53th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-8237?

CVE-2026-8237 is classified as CWE-862 (CWE-862). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2026-8237?

A Nuclei detection template exists for CVE-2026-8237, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2026-8237 published, and has it been updated?

CVE-2026-8237 was published on May 21, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2026-8237 — concrete5/concrete5

CVE-2026-8237 is a CWE-862 vulnerability in concrete5/concrete5. A fix is available for concrete5/concrete5 — see the affected versions and patch details below.

Concrete CMS 9.5.0 and below is vulnerable to IDOR in the`/ccm/frontend/conversations/message_detail` endpoint

Also known asGHSA-xpgc-7vc2-8725

Published

May 21, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-8237.

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐘concrete5/concrete5

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Concrete CMS 9.5.0 and below is vulnerable to IDOR. The /ccm/frontend/conversations/message_detail endpoint returns the full content of any conversation message. An unauthenticated attacker can enumerate all conversation messages, including messages from restricted pages, member-only areas, and the moderation queue. File attachments with download URLs are also exposed. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 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 Eldudareeno for reporting.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`concrete5/concrete5`	all versions	9.5.1`composer require concrete5/concrete5:^9.5.1`

Affected Products

1 product · 1 configurations

Application

concrete cmsconcretecms

< 9.5.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for concrete5/concrete5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update concrete5/concrete5 to 9.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-8237 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

How to detect CVE-2026-8237

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2026-8237 -u https://target

Template: Concrete CMS <= 9.5.0 - Unauthenticated Conversation Message Disclosure (IDOR)
Severity: medium
Impact: Unauthenticated attackers can access restricted conversation messages and file attachments, exposing sensitive information.
Remediation: Update to a version later than 9.5.0 or the latest available version

Template by ProjectDiscovery nuclei-templates (Pauullamm), MIT licensed. View the full template. Scan only systems you are authorised to test.

Frequently Asked Questions

Concrete CMS 9.5.0 and below is vulnerable to IDOR. The `/ccm/frontend/conversations/message_detail` endpoint returns the full content of any conversation message. An unauthenticated attacker can enumerate all conversation messages, including messages from restricted pages, member-only areas, and the moderation queue. File attachments with download URLs are also exposed. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 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 Eldudareeno for reporting.

O3 Security · Impact-Aware SCA

Is CVE-2026-8237 in your dependencies?

Find it across Packagist, including transitive dependencies.

Scan my dependencies How O3 SCA works