CVE-2026-8426 Details
Concrete CMS 9.5.0 and below does not validate a CSRF token before processing requests to /dashboard/extend/update/prepare_remote_upgrade/. An attacker who controls the remote package returned for a known marketplace item ID can overwrite the package PHP on disk and force its upgrade() method to execute in a single browser navigation. This results in remote code execution as the web server user.   In order to be vulnerable, the victim must be passing canInstallPackages, victim site must be connected to the Concrete marketplace; and the attacker controls the package returned for a marketplace item ID already installed on the victim site. 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.
View at NVD
Exploit prediction scoring system (EPSS) score for CVE-2026-8426
EPSS (Exploit Prediction Scoring System): EPSS predicts the likelihood that a vulnerability will be exploited in the wild. A higher percentage means a greater chance of an exploit occurring. The EPSS model produces a probability score between 0 and 1 (0 and 100%).
0.17 Probability of exploitation activity being observed over the next 30 days (7th percentile)
CVSS score for CVE-2026-8426
CVSS (Common Vulnerability Scoring System): An open framework owned and managed by FIRST.Org, Inc. that assigns a numerical score from 0 to 10 to software vulnerabilities to indicate their severity.
8.8 High
Products affected by CVE-2026-8426
ConcreteCMS 5.7.5.1
ConcreteCMS 5.7.5.10
ConcreteCMS 5.7.5.11
ConcreteCMS 5.7.5.12
ConcreteCMS 5.7.5.13
DVE Score by Bitsight AI
DVE scores complement traditional static scoring systems like CVSS with Bitsight AI powered real-time threat intelligence and underground cyber criminal activity so that security teams can reduce alert fatigue and focus on vulnerabilities most likely to be exploited.
Low
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CVE-2026-8426 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
US 5,527 38.00%
DE 1,898 13.05%
JP 1,399 9.62%
GB 1,304 8.97%
NL 660 4.54%
CA 603 4.15%
PL 421 2.89%
FR 392 2.70%
AU 339 2.33%
CH 332 2.28%

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CVE-2026-8426 Industry Footprint

Top 10 Identified Industries

*Service provider organizations (typically Technology and Telecommunications) are disproportionally represented in the results given their upstream ownership of end-user infrastructure. See our FAQs.

Industry* Observations Percentage
Technology 11,463 88.74%
Telecommunications 1,070 8.28%
Education 126 0.98%
Business Services 90 0.70%
Media/Entertainment 60 0.46%
Government/Politics 23 0.18%
Healthcare/Wellness 14 0.11%
Transportation 12 0.09%
Energy/Resources 12 0.09%
Manufacturing 11 0.09%

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