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GHSA-2r6j-862c-m2v2 BIT-typo3-2021-21355 CVE-2021-21355

Unrestricted File Upload in Form Framework

High Packagist
Severity
8.6 / 10
High · CVSS 3.1
Exploit chance (EPSS)
1.63%
Chance of exploitation in the next 30 days. Higher than 76.24% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-434 Unrestricted Upload of File with Dangerous Type
CWE-552 Files or Directories Accessible to External Parties
Fix
Available
3 packages have a fixed version

Description

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

Affected versions

Packagist

PackageVulnerableFixed in
typo3/cms
>= 10.0.0, < 10.4.14
10.4.14
typo3/cms
>= 11.0.0, < 11.1.1
11.1.1
typo3/cms
>= 9.0.0, < 9.5.25
9.5.25
typo3/cms-core
>= 10.0.0, < 10.4.14
10.4.14
typo3/cms-core
>= 11.0.0, < 11.1.1
11.1.1
typo3/cms-core
>= 9.0.0, < 9.5.25
9.5.25
typo3/cms-form
>= 8.0.0, < 8.7.40
8.7.40
typo3/cms-form
>= 9.0.0, < 9.5.25
9.5.25
typo3/cms-form
>= 10.0.0, < 10.4.14
10.4.14
typo3/cms-form
>= 11.0.0, < 11.1.1
11.1.1

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

typo3/cms Packagist → 10.4.14

composer
composer require typo3/cms:^10.4.14

typo3/cms-core Packagist → 10.4.14

composer
composer require typo3/cms-core:^10.4.14

typo3/cms-form Packagist → 8.7.40

composer
composer require typo3/cms-form:^8.7.40

Severity breakdown

CVSS 3.1 8.6

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L/E:F/RL:O/RC:C

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
Low
Exploit maturity
F

Weakness

CWE-434: Unrestricted Upload of File with Dangerous Type

The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.

How to prevent it
  • Architecture and Design: Generate a new, unique filename for an uploaded file instead of using the user-supplied filename, so that no external input is used at all.[REF-422] [REF-423]
  • Architecture and Design: When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
  • Architecture and Design: Consider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically. [REF-423]
  • Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. For example, limiting filenames to alphanumeric characters can help to restrict the introduction of unintended file extensions.
  • Architecture and Design: Define a very limited set of allowable extensions and only generate filenames that end in these extensions. Consider the possibility of XSS (CWE-79) before allowing .html or .htm file types.
  • Implementation: Ensure that only one extension is used in the filename. Some web servers, including some versions of Apache, may process files based on inner extensions so that "filename.php.gif" is fed to the PHP interpreter.[REF-422] [REF-423]
  • Implementation: When running on a web server that supports case-insensitive filenames, perform case-insensitive evaluations of the extensions that are provided.
  • Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
  • Implementation: Do not rely exclusively on sanity checks of file contents to ensure that the file is of the expected type and size. It may be possible for an attacker to hide code in some file segments that will still be executed by the server. For example, GIF images may contain a free-form comments field.
  • Implementation: Do not rely exclusively on the MIME content type or filename attribute when determining how to render a file. Validating the MIME content type and ensuring that it matches the extension is only a partial solution.
  • Architecture and Design, Operation: Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
  • Architecture and Design, Operation: Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software. OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations. This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise. Be careful to avoid CWE-243 and other weaknesses related to jails.

CWE-552: Files or Directories Accessible to External Parties

The product makes files or directories accessible to unauthorized actors, even though they should not be.

How to prevent it
  • Implementation, System Configuration, Operation: When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to disable public access.

References

Advisories

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-68jx-f42c-7599
TYPO3 CMS - Broken Access Control in Backend and Install Tool
High Also affects typo3/cms-core
GHSA-chm7-4vch-h8vr
TYPO3 CMS has Broken Access Control in its Media Module
High Also affects typo3/cms-core
GHSA-jh32-v29g-68pq
TYPO3 CMS has Privilege Escalation & SQL Injection in its Form Framework
High Also affects typo3/cms-core
GHSA-c78m-c52x-jgwp
TYPO3 CMS has Insecure Deserialization via Core API
Medium Also affects typo3/cms-core
GHSA-jf56-v8jc-jcc5
TYPO3 CMS has Broken Access Control in its File Abstraction Layer
Low Also affects typo3/cms-core
GHSA-2j54-93q2-3hjq
TYPO3 CMS has Broken Access Control in Backend API
Medium Also affects typo3/cms-core
GHSA-q93m-25xv-94hh
TYPO3 CMS: Broken Access Control in Media Module
Medium Also affects typo3/cms-core
GHSA-qcmw-6rm2-5x78
TYPO3 CMS has Broken Access Control in its DataHandler
Medium Also affects typo3/cms-core
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