CVE-2021-21357
8.3 · HIGHOverview
CVE-2021-21357 is a high-severity vulnerability affecting typo3 typo3. It was published on March 23, 2021 and has a CVSS 3.1 base score of 8.3 (HIGH).
This vulnerability has a CVSS 3.1 base score of 8.3, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
Technical Description
TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 8.7.40, 9.5.25, 10.4.14, 11.1.1 due to improper input validation, attackers can by-pass restrictions of predefined options and submit arbitrary data in the Form Designer backend module of the Form Framework. In the default configuration of the Form Framework this allows attackers to explicitly allow arbitrary mime-types for file uploads - however, default _fileDenyPattern_ successfully blocked files like _.htaccess_ or _malicious.php_. Besides that, attackers can persist those files in any writable directory of the corresponding TYPO3 installation. A valid backend user account with access to the form module is needed to exploit this vulnerability. This is fixed in versions 8.7.40, 9.5.25, 10.4.14, 11.1.1.
Remediation
Check the references section for vendor advisories and patches from typo3. Update typo3 to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| typo3 | typo3 | >= 8.0.0, < 8.7.40 | Affected |
References
Frequently Asked Questions
What is CVE-2021-21357?
CVE-2021-21357 is a high-severity vulnerability affecting typo3 typo3. It was published on March 23, 2021 and has a CVSS 3.1 base score of 8.3 (HIGH).
How severe is CVE-2021-21357?
This vulnerability has a CVSS 3.1 base score of 8.3, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
How do I fix or remediate CVE-2021-21357?
Check the references section for vendor advisories and patches from typo3. Update typo3 to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2021-21357?
CyberStrike's AI-powered security agents can automatically detect CVE-2021-21357 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
Automated penetration testing that runs continuously, not just quarterly.
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Browser-based exploitation validates findings with real proof-of-concept.
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