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CVE-2021-21359

Denial of Service in Page Error Handling

5.9 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

1.73%Up 0.8 points since Apr 14, 2021
90%50%10%1%

What each source reports

CVE List Score used 5.9

Denial of Service in Page Error Handling

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.

Record
CVE-2021-21359
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-674, CWE-405
Updated
2026-11-02
EUVDEUVD-2021-0598 5.9

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.

Record
EUVD-2021-0598
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-03
GitHub AdvisoriesGHSA-4p9g-qgx9-397p 5.5

Denial of Service in Page Error Handling

Meta

  • CVSS: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C (5.5)
  • CWE-405, CWE-674
  • Status: DRAFT

Problem

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.

Solution

Update to TYPO3 versions 9.5.25, 10.4.14, 11.1.1 that fix the problem described.

Credits

Thanks to Paul Keller, Mathias Bolt Lesniak and Kay Strobach who reported this issue and to TYPO3 framework merger Frank Nägler and to TYPO3 security team member Torben Hansen who fixed the issue.

References

Record
GHSA-4p9g-qgx9-397p
CVSS 3.1
5.5 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C
Weakness
CWE-405, CWE-674
Updated
2026-11-02
NVD 5.9

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.

Record
CVE-2021-21359
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness
CWE-405, CWE-674
Updated
2026-11-02
OSV 7.5

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.

Record
CVE-2021-21359
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVGHSA-4p9g-qgx9-397p 5.9

Denial of Service in Page Error Handling

Meta

  • CVSS: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C (5.5)
  • CWE-405, CWE-674
  • Status: DRAFT

Problem

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.

Solution

Update to TYPO3 versions 9.5.25, 10.4.14, 11.1.1 that fix the problem described.

Credits

Thanks to Paul Keller, Mathias Bolt Lesniak and Kay Strobach who reported this issue and to TYPO3 framework merger Frank Nägler and to TYPO3 security team member Torben Hansen who fixed the issue.

References

Record
GHSA-4p9g-qgx9-397p
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H/E:F/RL:O/RC:C
Weakness
CWE-405, CWE-674
Updated
2026-11-02
OSVBIT-typo3-2021-21359 No score

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.

Record
BIT-typo3-2021-21359
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
typo3/cms-core
Packagist
10.0.0 up to 10.4.14
10.4.14
typo3/cms-core
Packagist
11.0.0 up to 11.1.1
11.1.1
typo3/cms-core
Packagist
9.0.0 up to 9.5.25
9.5.25
typo3/cms
Packagist
10.0.0 up to 10.4.14
10.4.14
typo3/cms
Packagist
11.0.0 up to 11.1.1
11.1.1
typo3/cms
Packagist
9.0.0 up to 9.5.25
9.5.25
typo3
Bitnami
9.0.0 up to 9.5.25, 10.0.0 up to 10.4.14, 11.0.0 up to 11.1.1
9.5.2510.4.1411.1.1
typo3/cms-core
Packagist
10.0.0 up to 10.4.14, plus listed versions
v10.0.0v10.1.0v10.2.0v10.2.1v10.2.2
Show 15 moreShow less
v10.3.0v10.4.0v10.4.1v10.4.10v10.4.11v10.4.12v10.4.13v10.4.2v10.4.3v10.4.4v10.4.5v10.4.6v10.4.7v10.4.8v10.4.9
10.4.14
typo3/cms-core
Packagist
11.0.0 up to 11.1.1, plus listed versions
v11.0.0v11.1.0
11.1.1
typo3/cms-core
Packagist
9.0.0 up to 9.5.25, plus listed versions
v9.0.0v9.1.0v9.2.0v9.2.1v9.3.0
Show 29 moreShow less
v9.3.1v9.3.2v9.3.3v9.4.0v9.5.0v9.5.1v9.5.10v9.5.11v9.5.12v9.5.13v9.5.14v9.5.15v9.5.16v9.5.17v9.5.18v9.5.19v9.5.2v9.5.20v9.5.21v9.5.22v9.5.23v9.5.24v9.5.3v9.5.4v9.5.5v9.5.6v9.5.7v9.5.8v9.5.9
9.5.25
typo3/cms
Packagist
10.0.0 up to 10.4.14, plus listed versions
v10.0.0v10.1.0v10.2.0v10.2.1v10.2.2
Show 15 moreShow less
v10.3.0v10.4.0v10.4.1v10.4.10v10.4.11v10.4.12v10.4.13v10.4.2v10.4.3v10.4.4v10.4.5v10.4.6v10.4.7v10.4.8v10.4.9
10.4.14
typo3/cms
Packagist
11.0.0 up to 11.1.1, plus listed versions
v11.0.0v11.1.0
11.1.1
typo3/cms
Packagist
9.0.0 up to 9.5.25, plus listed versions
v9.0.0v9.1.0v9.2.0v9.2.1v9.3.0
Show 29 moreShow less
v9.3.1v9.3.2v9.3.3v9.4.0v9.5.0v9.5.1v9.5.10v9.5.11v9.5.12v9.5.13v9.5.14v9.5.15v9.5.16v9.5.17v9.5.18v9.5.19v9.5.2v9.5.20v9.5.21v9.5.22v9.5.23v9.5.24v9.5.3v9.5.4v9.5.5v9.5.6v9.5.7v9.5.8v9.5.9
9.5.25

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-21359 is a medium vulnerability (CVSS 5.9) in Typo3, published March 23, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.73%, the 77th percentile. Fixed in typo3/cms-core 10.4.14.

References

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