CVE-2026-8421— Concrete CMS 9.5.0 and below is vulnerable to CSRF on install_package() with conditional token bypass leading to RCE
Possible ATT&CK Techniques 3AI
T1078 · Valid Accounts T1059 · Command and Scripting Interpreter T1190 · Exploit Public-Facing ApplicationAffected Version Matrix 1
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Concrete CMS | Concrete CMS | 5.0≤ 9.5.0 | affected |
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I. Basic Information for CVE-2026-8421
Vulnerability Information
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Vulnerability Title
Concrete CMS 9.5.0 and below is vulnerable to CSRF on install_package() with conditional token bypass leading to RCE
Source: NVD (National Vulnerability Database)
Vulnerability Description
Concrete CMS 9.5.0 and below contains a CSRF vulnerability in the install_package() method of concrete/controllers/single_page/dashboard/extend/install.php. An attacker who can cause an authenticated administrator to visit a crafted page, and who has placed or caused a package to be present under DIR_PACKAGES/<handle>/, can force the installation of that package without any CSRF protection. Package installation executes the package controller's install() method as the web server user, enabling remote code execution. In order to be vulnerable, the victim must be passing canInstallPackages. 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.
Source: NVD (National Vulnerability Database)
CVSS Information
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Type
跨站请求伪造(CSRF)
Source: NVD (National Vulnerability Database)
Vulnerability Title
Concrete CMS 跨站请求伪造漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Concrete CMS是Concrete CMS开源的一个面向团队的开源内容管理系统。 Concrete CMS 9.5.0及之前版本存在跨站请求伪造漏洞，该漏洞源于install_package()方法存在CSRF漏洞，可能导致攻击者强制安装包并执行远程代码。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Concrete CMS | Concrete CMS | 5.0 ~ 9.5.0 | - |
II. Public POCs for CVE-2026-8421
| # | POC Description | Source Link | Shenlong Link |
|---|
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Vendor Pages for CVE-2026-8421 (1)
- 🔗 9.5.1 Release Notes :: Concrete CMSrelease-notes
Same Patch Batch · Concrete CMS · 2026-05-21 · 41 CVEs total
| CVE-2026-8240 | Concrete CMS 9.5.0 and below is vulnerable to unauthenticated page metadata disclosure in | |
| CVE-2026-8416 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8412 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8237 | Concrete CMS 9.5.0 and below is vulnerable to IDOR in the`/ccm/frontend/conversations/mess | |
| CVE-2026-8434 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8435 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8414 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8433 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8239 | Concrete CMS 9.5.0 and below is vulnerable to IDOR in '/ccm/frontend/conversations/get_rat | |
| CVE-2026-8411 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8432 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8236 | Concrete CMS 9.5.0 and below is vulnerable to IDOR combined with a missing authentication | |
| CVE-2026-8413 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8415 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8427 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete | |
| CVE-2026-8238 | Concrete CMS 9.5.0 and below is vulnerable to IDOR in '/ccm/frontend/conversations/message | |
| CVE-2026-8245 | Concrete CMS 9.5.0 and below is vulnerable to Reflected XSS in Legacy Pagination via HTML | |
| CVE-2026-7890 | Concrete CMS 9.5.0 is vulnerable to SSRF via RSS Displayer Block | |
| CVE-2026-8139 | Concrete CMS 9.5.0 and below is vulnerable to Stored XSS via external-link page cvName | |
| CVE-2026-8409 | Concrete CMS 9 before 9.5.0 is vulnerable to Cross Site Request Forgery (CSRF) at concrete |
Showing top 20 of 41 CVEs. View all on vendor page → →
IV. Related Vulnerabilities
Same product: Concrete CMS
- CVE-2026-8353
Concrete CMS version 9.0 to 9.5.0 is vulnerable to Stored XS - CVE-2026-8347
Concrete CMS 9.5.0 and below is vulnerable to IDOR + wrong-a - CVE-2026-8340
Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backe - CVE-2026-8139
Concrete CMS 9.5.0 and below is vulnerable to Stored XSS via - CVE-2026-7890
Concrete CMS 9.5.0 is vulnerable to SSRF via RSS Displayer B
Same vendor: Concrete CMS
- CVE-2026-8353
Concrete CMS version 9.0 to 9.5.0 is vulnerable to Stored XS - CVE-2026-8347
Concrete CMS 9.5.0 and below is vulnerable to IDOR + wrong-a - CVE-2026-8340
Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backe - CVE-2026-8139
Concrete CMS 9.5.0 and below is vulnerable to Stored XSS via - CVE-2026-7890
Concrete CMS 9.5.0 is vulnerable to SSRF via RSS Displayer B
Same weakness: CWE-352
- CVE-2026-8906
WP Promoter <= 1.3 - Cross-Site Request Forgery to Stored Cr - CVE-2026-8942
MetaMagic SEO Plugin <= 1.6 - Cross-Site Request Forgery to - CVE-2026-49001
Cross-Site Request Forgery (CSRF) vulnerability in ZTE ZXUni - CVE-2026-8708
Genzel breadcrumbs <= 1.2 - Cross-Site Request Forgery to Se - CVE-2026-7614
Old Posts Highlighter <= 1.0.3 - Cross-Site Request Forgery
V. Comments for CVE-2026-8421
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