CVE-2021-21355: Malicious File Upload
First published: Tue Mar 16 2021(Updated: )
### Problem Due to the lack of ensuring file extensions belong to configured allowed mime-types, attackers can upload arbitrary data with arbitrary file extensions - however, default _fileDenyPattern_ successfully blocked files like _.htaccess_ or _malicious.php_. TYPO3 Extbase extensions, which implement a file upload and do not implement a custom _TypeConverter_ to transform uploaded files into _FileReference_ domain model objects are affected by the vulnerability as well, since the _UploadedFileReferenceConverter_ of _ext:form_ handles the file upload and will accept files of any mime-type which are persisted to 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. ### Solution Update to TYPO3 versions 8.7.40, 9.5.25, 10.4.14, 11.1.1 that fix the problem described. Type converter _UploadedFileReferenceConverter_ is not registered globally anymore and just handles uploaded files within the scope of the Form Framework. Guessable storage location has changed from _/fileadmin/user_upload/form\_\<random-hash\>/_ to _/fileadmin/form_uploads/<random-40-bit>_. Allowed mime-types must match expected file extensions (e.g. _application/pdf_ must be _.pdf_, and cannot be _.html_). Extbase extensions, who rely on the global availability of the _UploadedFileReferenceConverter_ must now implement a custom _TypeConverter_ to handle file uploads or explicitly implement the ext:form _UploadedFileReferenceConverter_ with appropriate setting for accepted mime-types. ### Credits Thanks to Sebastian Michaelsen, Marc Lindemann, Oliver Eglseder, Markus Volkmer, Jakob Kunzmann, Johannes Regner, Richie Lee who reported this issue, and to TYPO3 core & security team members Oliver Hader & Benni Mack, as well as TYPO3 contributor Ralf Zimmermann who fixed the issue. ### References * [TYPO3-CORE-SA-2021-002](https://typo3.org/security/advisory/typo3-core-sa-2021-002)
Credit: security-advisories@github.com security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| composer/typo3/cms | >=10.0.0<10.4.14>=11.0.0<11.1.1>=9.0.0<9.5.25 | |
| composer/typo3/cms-core | >=10.0.0<10.4.14>=11.0.0<11.1.1>=9.0.0<9.5.25 | |
| Typo3 Typo3 | >=8.0.0<8.7.40 | |
| Typo3 Typo3 | >=9.0.0<9.5.25 | |
| Typo3 Typo3 | >=10.0.0<10.4.14 | |
| Typo3 Typo3 | >=11.0.0<11.1.1 | |
| composer/typo3/cms | >=9.0.0<9.5.25 | 9.5.25 |
| composer/typo3/cms | >=11.0.0<11.1.1 | 11.1.1 |
| composer/typo3/cms | >=10.0.0<10.4.14 | 10.4.14 |
| composer/typo3/cms-core | >=9.0.0<9.5.25 | 9.5.25 |
| composer/typo3/cms-core | >=11.0.0<11.1.1 | 11.1.1 |
| composer/typo3/cms-core | >=10.0.0<10.4.14 | 10.4.14 |
| composer/typo3/cms-form | >=11.0.0<=11.1.0 | 11.1.1 |
| composer/typo3/cms-form | >=10.0.0<=10.4.13 | 10.4.14 |
| composer/typo3/cms-form | >=9.0.0<=9.5.24 | 9.5.25 |
| composer/typo3/cms-form | >=8.0.0<=8.7.39 | 8.7.40 |
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Reference Links
- https://typo3.org/security/advisory/typo3-core-sa-2021-002
- https://github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-2r6j-862c-m2v2
- https://packagist.org/packages/typo3/cms-form
- https://nvd.nist.gov/vuln/detail/CVE-2021-21355
- https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms-core/CVE-2021-21355.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/typo3/cms/CVE-2021-21355.yaml
- https://github.com/advisories/GHSA-2r6j-862c-m2v2 (Advisory)
Frequently Asked Questions
What is the vulnerability ID of this TYPO3 vulnerability?
The vulnerability ID is CVE-2021-21355.
What is the severity level of CVE-2021-21355?
The severity level of CVE-2021-21355 is high.
Which versions of TYPO3 are affected by this vulnerability?
Versions 8.7.40, 9.5.25, 10.4.14, and 11.1.1 of TYPO3 are affected by this vulnerability.
Is there a fix available for CVE-2021-21355?
Yes, there are fixes available for CVE-2021-21355. Please refer to the official TYPO3 security advisory for more information.
Where can I find more information about this vulnerability?
You can find more information about this vulnerability in the TYPO3 security advisory and the GitHub security advisory mentioned in the references.
- collector/friends-of-php
- collector/nvd-index
- agent/type
- agent/first-publish-date
- collector/github-advisory-latest
- source/GitHub
- alias/GHSA-2r6j-862c-m2v2
- alias/CVE-2021-21355
- agent/software-canonical-lookup
- agent/severity
- agent/weakness
- agent/references
- agent/last-modified-date
- agent/author
- agent/tags
- agent/description
- collector/nvd-cve
- source/NVD
- agent/softwarecombine
- agent/event
- collector/github-advisory
- package-manager/composer
- vendor/typo3
- canonical/typo3 typo3
- version/typo3 typo3/8.0.0
- version/typo3 typo3/9.0.0
- version/typo3 typo3/10.0.0
- version/typo3 typo3/11.0.0