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| Vulnerability ID | VCID-fbhh-atu7-e3da |
| Aliases |
CVE-2021-21355
GHSA-2r6j-862c-m2v2 |
| Summary | Unrestricted File Upload in Form Framework ### 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) |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 8.0 |
| Risk | 4.0 |
| Affected and Fixed Packages | Package Details |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Exploitability (E) | Access Vector (AV) | Access Complexity (AC) | Authentication (Au) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|
high functional unproven proof_of_concept not_defined |
local adjacent_network network |
high medium low |
multiple single none |
none partial complete |
none partial complete |
none partial complete |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Percentile | 0.6082 |
| EPSS Score | 0.00416 |
| Published At | June 30, 2025, 12:55 p.m. |
| Date | Actor | Action | Source | VulnerableCode Version |
|---|---|---|---|---|
| 2025-07-01T12:19:10.321747+00:00 | GithubOSV Importer | Import | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/03/GHSA-2r6j-862c-m2v2/GHSA-2r6j-862c-m2v2.json | 36.1.3 |