CVE-2021-21359

Name: CVE-2021-21359
Creator: NVD / NIST
Published: 2021-03-23T02:15:12.893+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.73%

Last modified Jun 17, 2026

CVE-2021-21359 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 1.73% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

1.73%

74.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Typo3	Typo3	>= 9.0.0, < 9.5.25
Typo3	Typo3	>= 10.0.0, < 10.4.14
Typo3	Typo3	>= 11.0.0, < 11.1.1

References

https://github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-4p9g-qgx9-397pThird Party Advisory
https://packagist.org/packages/typo3/cms-coreRelease Notes, Third Party Advisory
https://typo3.org/security/advisory/typo3-core-sa-2021-005Vendor Advisory
https://github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-4p9g-qgx9-397pThird Party Advisory
https://packagist.org/packages/typo3/cms-coreRelease Notes, Third Party Advisory
https://typo3.org/security/advisory/typo3-core-sa-2021-005Vendor Advisory

Timeline

Published: Mar 23, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21359?

How severe is CVE-2021-21359?

CVE-2021-21359 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.73% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21359?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21359?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST