CVE-2021-21357
No exploitation reported by the sources we read.
- Published2021-03-23
- Fixed in11.1.1 · 10.4.14 · 9.5.25 · 8.7.40
- WeaknessCWE-20 · CWE-22 · CWE-434
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
Description
TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 8.7.40, 9.5.25, 10.4.14, 11.1.1 due to improper input validation, attackers can by-pass restrictions of predefined options and submit arbitrary data in the Form Designer backend module of the Form Framework. In the default configuration of the Form Framework this allows attackers to explicitly allow arbitrary mime-types for file uploads - however, default _fileDenyPattern_ successfully blocked files like _.htaccess_ or _malicious.php_. Besides that, attackers can persist those files in any writable directory of the corresponding TYPO3 installation. A valid backend user account with access to the form module is needed to exploit this vulnerability. This is fixed in versions 8.7.40, 9.5.25, 10.4.14, 11.1.1.
Timeline
dates in UTC- 2021-03-2302:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 18:48 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-21357?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-21357?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 11.x | ≥ 11.0.0, < 11.1.1 | 11.1.1 | NVD |
| 10.x | ≥ 10.0.0, < 10.4.14 | 10.4.14 | NVD |
| 9.x | ≥ 9.0.0, < 9.5.25 | 9.5.25 | NVD |
| 8.x | ≥ 8.0.0, < 8.7.40 | 8.7.40 | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
- Update Typo3 to 11.1.1 · 10.4.14 · 9.5.25 · 8.7.40
Advisories and patches
- packagist.orgRelease Notes
- typo3.orgVendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- CNACVSS 3.18.3read 2026-10-23
- NVDCVSS 3.18.3read 2026-10-23
- NVDCVSS 2.06.5read 2026-10-23
- CNAweakness (CWE)CWE-20, CWE-22, CWE-434read 2026-10-23
- FIRST EPSSEPSS score1.6 %2026-10-22
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H
- Published
- 2021-03-23
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-21357?
Is CVE-2021-21357 actively exploited?
What is the CVSS score for CVE-2021-21357?
Hear about the next vulnerability in your software
Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».
No credit card required · No monthly cap on website lookups · 250 API requests/month
Go further
- Following what attackers exploit right now? The CISA KEV additions of the month, with their patch deadlines.
- Running this software? Vulnerability monitoring alerts you to new vulnerabilities in your products.
Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.