CVE-2021-21355
Published: 23 March 2021
Summary
CVE-2021-21355 is a high-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability in Typo3 Typo3. Its CVSS base score is 8.6 (High).
Operationally, ranked in the top 37.8% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-0587
Vulnerability details
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 the lack of ensuring file extensions belong to configured allowed mime-types, attackers can upload arbitrary data with arbitrary file…
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extensions - however, default _fileDenyPattern_ successfully blocked files like _.htaccess_ or _malicious.php_. Besides that, _UploadedFileReferenceConverter_ transforming uploaded files into proper FileReference domain model objects handles possible file uploads for other extensions as well - given those extensions use the Extbase MVC framework, make use of FileReference items in their direct or inherited domain model definitions and did not implement their own type converter. In case this scenario applies, _UploadedFileReferenceConverter_ accepts any file mime-type and persists files in the default location. In any way, uploaded files are placed in the default location _/fileadmin/user_upload/_, in most scenarios keeping the submitted filename - which allows attackers to directly reference files, or even correctly guess filenames used by other individuals, disclosing this information. No authentication is required to exploit this vulnerability. This is fixed in versions 8.7.40, 9.5.25, 10.4.14, 11.1.1.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Controls on authorized publication limit files and directories with nonpublic data from becoming accessible to external parties.
Controlling and documenting P2P file sharing prevents files and directories from being made accessible to external parties for unauthorized distribution.
Identifying and documenting file and directory locations allows restriction of access to external parties.
Protecting backup files ensures they are not accessible to external parties or unauthorized spheres.
Sanitizing equipment before off-site maintenance reduces the risk of files or directories containing sensitive data becoming accessible to external parties.
Policy restricts media access to authorized parties only, preventing exposure of resources to external or unauthorized actors.
Media access restrictions prevent files or directories from being accessible to external parties.
Requiring identifiable owners for portable devices reduces the attack surface for unrestricted uploads of dangerous file types via anonymous media.