CVE-2021-21355 is a vulnerability in TYPO3
Published on March 23, 2021
Unrestricted File Upload in Form Framework
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 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.
Vulnerability Analysis
CVE-2021-21355 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a high impact on integrity, and a small impact on availability.
Weakness Types
What is an Unrestricted File Upload Vulnerability?
The software allows the attacker to upload or transfer files of dangerous types that can be automatically processed within the product's environment.
CVE-2021-21355 has been classified to as an Unrestricted File Upload vulnerability or weakness.
Files or Directories Accessible to External Parties
The product makes files or directories accessible to unauthorized actors, even though they should not be. Web servers, FTP servers, and similar servers may store a set of files underneath a "root" directory that is accessible to the server's users. Applications may store sensitive files underneath this root without also using access control to limit which users may request those files, if any. Alternately, an application might package multiple files or directories into an archive file (e.g., ZIP or tar), but the application might not exclude sensitive files that are underneath those directories.
Products Associated with CVE-2021-21355
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Affected Versions
TYPO3.CMS:- Version >= 8.0.0, <= 8.7.39 is affected.
- Version >= 9.0.0, <= 9.5.24 is affected.
- Version >= 10.0.0, <= 10.4.13 is affected.
- Version >= 11.0.0, <= 11.1.0 is affected.
Vulnerable Packages
The following package name and versions may be associated with CVE-2021-21355
| Package Manager | Vulnerable Package | Versions | Fixed In |
|---|---|---|---|
| composer | typo3/cms-form | >= 8.0.0, <= 8.7.39 | 8.7.40 |
| composer | typo3/cms-form | >= 9.0.0, <= 9.5.24 | 9.5.25 |
| composer | typo3/cms-form | >= 10.0.0, <= 10.4.13 | 10.4.14 |
| composer | typo3/cms-form | >= 11.0.0, <= 11.1.0 | 11.1.1 |
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.