CVE-2026-81910 Details
Concrete CMS 9 through 9.5.2 is vulnerable to Server-Side Template Injection (SSTI) in Theme Customizer via Unvalidated Style Values. Values submitted through the customizer (color channels and other style properties handled by ColorStyle and sibling Style classes such as FontFamilyStyle and ImageStyle) are interpolated into server-compiled LESS source without neutralization of LESS syntax, allowing a user with the Theme Customization permission to inject arbitrary LESS directives. By injecting the @import (inline) directive, an attacker can read arbitrary files on the server and reach internal network resources through PHP stream wrappers. The compiled output, including any disclosed file contents, is written to the site's publicly served CSS cache, exposing database credentials, private keys, and other application secrets, and enabling server-side request forgery. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 5.9 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.
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Exploit prediction scoring system (EPSS) score for CVE-2026-81910
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%).
0.24 Probability of exploitation activity being observed over the next 30 days (16th percentile)
CVSS score for CVE-2026-81910
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.
6.5 Medium
Products affected by CVE-2026-81910
ConcreteCMS 9.4.7
ConcreteCMS 9.4.8
ConcreteCMS 9.5.1
ConcreteCMS 9.5.2
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-2026-81910 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
US 100 60.61%
DE 22 13.33%
JP 12 7.27%
GB 6 3.64%
NL 6 3.64%
TR 5 3.03%
IE 3 1.82%
PL 3 1.82%
AT 2 1.21%
FR 2 1.21%

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CVE-2026-81910 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 149 93.13%
Telecommunications 4 2.50%
Education 3 1.88%
Business Services 2 1.25%
Finance 1 0.63%
Government/Politics 1 0.63%

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