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GHSA-prxr-vjgc-2cq9 — concrete5/concrete5

GHSA-prxr-vjgc-2cq9 is a Cross-Site Request Forgery (CSRF) vulnerability in concrete5/concrete5. A fix is available for concrete5/concrete5 — see the affected versions and patch details below.

Concrete CMS is Vulnerable to Cross-Site Request Forgery

Also known asCVE-2026-8428
Published
May 21, 2026
Updated
Sep 10, 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

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • 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 GHSA-prxr-vjgc-2cq9.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs8th percentile — riskier than 8% of all scored CVEsHighest risk
0.00%0.23%0.46%0.69%0.0%0.1%0.1%0.2%0.2%Jun 26Sep 26Oct 26

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 emits a CSRF token in the local_available_update.php view ($token->output('do_update')) but the corresponding do_update() method in concrete/controllers/single_page/dashboard/system/update/update.php never calls $this->token->validate('do_update'). The form is rendered as a POST form, meaning the token reaches the browser, but because the controller discards it without verification, an attacker can craft a cross-site POST that triggers a core CMS update to an attacker-specified version string.  In order to be vulnerable, theictim must be passing canUpgrade()anda valid update version must be present under DIR_CORE_UPDATES. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 7.5 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks https://github.com/maru1009 for reporting.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistconcrete5/concrete5all versions9.5.1composer 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
  1. 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.

  2. Fix

    Update concrete5/concrete5 to 9.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-prxr-vjgc-2cq9 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Concrete CMS 9.5.0 and below emits a CSRF token in the local_available_update.php view ($token->output('do_update')) but the corresponding do_update() method in concrete/controllers/single_page/dashboard/system/update/update.php never calls $this->token->validate('do_update'). The form is rendered as a POST form, meaning the token reaches the browser, but because the controller discards it without verification, an attacker can craft a cross-site POST that triggers a core CMS update to an attacker-specified version string.  In order to be vulnerable, theictim must be passing canUpgrade()anda va
O3 Security · Impact-Aware SCA

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GHSA-prxr-vjgc-2cq9: CSRF — Fixed in 9.5.1 | O3 Security