CVE-2020-26227 — cms-core
MEDIUMCVE-2020-26227 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in typo3/cms-core. 2 public exploit references exist, so weaponization risk is real. A fix is available for typo3/cms-core — see the affected versions and patch details below.
Cross-Site Scripting in Fluid view helpers
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2020-26227 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
typo3/cms-core🐘typo3/cms-core🐘typo3/cms-core🐘typo3/cms🐘typo3/cms🐘typo3/cmsReal-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
Meta
- CVSS:
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N/E:F/RL:O/RC:C(5.7)- CWE-79
Problem
It has been discovered that system extension Fluid (typo3/cms-fluid) of the TYPO3 core is vulnerable to cross-site scripting passing user-controlled data as argument to Fluid view helpers.
<f:form ... fieldNamePrefix="{payload}" />
<f:be.labels.csh ... label="{payload}" />
<f:be.menus.actionMenu ... label="{payload}" />
Solution
Update to TYPO3 versions 9.5.23 or 10.4.10 that fix the problem described.
Credits
Thanks to TYPO3 security team member Oliver Hader who reported this issue and to TYPO3 security team members Helmut Hummel & Oliver Hader who fixed the issue.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | typo3/cms-core | ≥ 9.0.0&&< 9.5.23 | 9.5.23composer require typo3/cms-core:^9.5.23 |
| 🐘Packagist | typo3/cms-core | ≥ 10.0.0&&< 10.4.10 | 10.4.10composer require typo3/cms-core:^10.4.10 |
| 🐘Packagist | typo3/cms-core | ≥ 8.7.0&&< 8.7.38 | 8.7.38composer require typo3/cms-core:^8.7.38 |
| 🐘Packagist | typo3/cms | ≥ 10.0.0&&< 10.4.10 | 10.4.10composer require typo3/cms:^10.4.10 |
| 🐘Packagist | typo3/cms | ≥ 9.0.0&&< 9.5.23 | 9.5.23composer require typo3/cms:^9.5.23 |
| 🐘Packagist | typo3/cms | ≥ 8.7.0&&< 8.7.38 | 8.7.38composer require typo3/cms:^8.7.38 |
Affected Products
typo3typo3Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for typo3/cms-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update typo3/cms-core to 9.5.23 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-26227 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is CVE-2020-26227 in your dependencies?
Find it across Packagist, including transitive dependencies.