CVE-2021-21359

Q: How do I fix CVE-2021-21359?

Upgrade typo3 to 11.1.1 or later.

Q: Is CVE-2021-21359 being actively exploited?

Not that we know of. CVE-2021-21359 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 1.7% is the estimated probability that it will be exploited in the next 30 days. That is higher than 75% of all scored CVEs.

Q: How severe is CVE-2021-21359?

CVE-2021-21359 has a CVSS v3 base score of 5.9, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2021-21359 affect?

Published advisories record a fix for typo3 (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

MEDIUMEPSS 75th pctl

5.9

CVSS v3

NVD

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.

CWE-405 CWE-674

How to fix

Remediation Available

typo3NVD

Affected:>= 11.0.0, < 11.1.1Fixed in:11.1.1CVE-2021-21359derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

1.73%probability of exploitation in 30 days

75thpercentile

Elevated risk: more likely to be exploited than 75% of all known CVEs.

References

Vendor Advisory1

typo3.org

Third-Party Advisory2

Related Vulnerabilities

Other CWE-405 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2019-11479	High	7.5	92%	-	Fix
CVE-2024-11187	High	7.5	15%	-	Fix
CVE-2025-8677	High	7.5	11%	-	Fix
CVE-2021-38447	High	8.6	2.1%	-	Fix
CVE-2018-15492	High	7.5	1.2%	-	-
CVE-2026-47774	High	7.5	1.0%	-	Fix

Common questions

How do I fix CVE-2021-21359?

Upgrade typo3 to 11.1.1 or later.

Is CVE-2021-21359 being actively exploited?

Not that we know of. CVE-2021-21359 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 1.7% is the estimated probability that it will be exploited in the next 30 days. That is higher than 75% of all scored CVEs.

How severe is CVE-2021-21359?

CVE-2021-21359 has a CVSS v3 base score of 5.9, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2021-21359 affect?

Published advisories record a fix for typo3 (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

Embed a live status badge for CVE-2021-21359

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.