CVE-2021-21359: TYPO3

High severity, CVSS 7.5. EPSS: 1.7% chance of exploitation in the next 30 days.

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 TYPO3: from 9.0.0, before 9.5.25 (fixed in 9.5.25); from 10.0.0, before 10.4.14 (fixed in 10.4.14); from 11.0.0, before 11.1.1 (fixed in 11.1.1)

Published 2021-03-23. Last modified 2026-06-17.