What’s Vulnerable › Vulnerabilities

CVE-2021-21359: Denial of Service in Page Error Handling

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-23 · updated 2026-06-17
• Weakness: CWE-405

Description

TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 9.5.25, 10.4.14, 11.1.1 requesting invalid or non-existing resources via HTTP triggers the page error handler which again could retrieve content to be shown as error message from another page. This leads to a scenario in which the application is calling itself recursively - amplifying the impact of the initial attack until the limits of the web server are exceeded. This is fixed in versions 9.5.25, 10.4.14, 11.1.1.

Affected products

• typo3: from 9.0.0 before 9.5.25; from 10.0.0 before 10.4.14; from 11.0.0 before 11.1.1 — fixed in 10.4.14, 11.1.1, 9.5.25

How to fix

Upgrade to a fixed version: typo3 10.4.14, 11.1.1, 9.5.25. Check the vendor advisory for mitigations.

References

• https://github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-4p9g-qgx9-397p
• https://packagist.org/packages/typo3/cms-core
• https://typo3.org/security/advisory/typo3-core-sa-2021-005
• https://github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-4p9g-qgx9-397p
• https://packagist.org/packages/typo3/cms-core
• https://typo3.org/security/advisory/typo3-core-sa-2021-005

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