What is CVE-2021-21340?

CVE-2021-21340 is a medium-severity vulnerability in TYPO3, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-03-23.

How severe is CVE-2021-21340?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in TYPO3

CVE-2021-21340

TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 10.4.14, 11.1.1 it has been discovered that database fields used as _descriptionColumn_ are vulnerable to cross-site scripting when their content gets previewed. A valid backend user account is needed to exploit this vulnerability. This is fixed in versions 10.4.14, 11.1.1 .

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-03-23 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.009 (57.3th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 57.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

TYPO3
TYPO3 Typo3.cms — versions >= 10.0.0, <= 10.4.13, >= 11.0.0, <= 11.1.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-fjh3-g8gq-9q92 (Third Party Advisory)
packagist.org/packages/typo3/cms-backend (Third Party Advisory, Release Notes)
typo3.org/security/advisory/typo3-core-sa-2021-007 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-21340?: CVE-2021-21340 is a medium-severity vulnerability in TYPO3, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-03-23.
How severe is CVE-2021-21340?: Medium severity. CVSS v3 base score is 5.4 out of 10.