Drupal core Un-restricted Upload of File
CVE-2020-13671 is a high-severity unrestricted upload of file with dangerous type vulnerability in Drupal Core from Drupal, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected Drupal Core versions: 9.0 versions prior to 9.0.8; 8.9 versions prior to 8.9.9; 8.8 versions prior to 8.8.11, and others listed below. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on January 18, 2022, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Drupal to 7.74 or 8.8.11 or 8.9.9 or 9.0.8, whichever matches your release line, or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on drupal.org for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Drupal | Drupal Core | 9.0 versions prior to 9.0.8; 8.9 versions prior to 8.9.9; 8.8 versions prior to 8.8.11; 7 versions prior to 7.74 | Not stated |
| Drupal | Drupal | 7.0 up to, but not including, 7.74; 8.8.0 up to, but not including, 8.8.11; 8.9.0 up to, but not including, 8.9.9; 9.0.0 up to, but not including, 9.0.8 | 7.74, 8.8.11, 8.9.9, 9.0.8 |
| Fedora Project | Fedora | 32; 33 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 8.8 | High | NVD |
| CVSS 3.1 | 8.8 | High | CISA (ADP) |
| CVSS 2.0 | 6.5 | Medium | NVD |
Official description
Drupal core does not properly sanitize certain filenames on uploaded files, which can lead to files being interpreted as the incorrect extension and served as the wrong MIME type or executed as PHP for certain hosting configurations. This issue affects: Drupal Drupal Core 9.0 versions prior to 9.0.8, 8.9 versions prior to 8.9.9, 8.8 versions prior to 8.8.11, and 7 versions prior to 7.74.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: 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 developers prevent this class of flaw
- 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.
- 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.
- Consider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically.
More Unrestricted Upload of File with Dangerous Type vulnerabilities (CWE-434)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-13671US Government Resource
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Recent Unrestricted Upload of File with Dangerous Type vulnerabilities
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- 8.8 High severity
- 6.5 Medium severity
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