Executive brief
Drupal is a popular open-source content management system used to build and manage websites. A security flaw in its image upload process allows users with upload permissions to bypass file type checks. This could allow an attacker to upload malicious files that, when viewed by other users or administrators, execute unauthorized scripts in their browser, potentially leading to data theft or account takeover.
Technical details
A Cross-Site Scripting (XSS) vulnerability exists in Drupal core's JSON:API and REST modules. The root cause is improper validation during image file uploads; while the system checks file extensions, it fails to validate the MIME type. An authenticated attacker with permissions to upload images can exploit this by uploading a non-image file (such as an HTML file with a deceptive extension). If the web server is configured to serve files based on their actual MIME type rather than the extension, the malicious script will execute in the context of the victim's browser. This issue is resolved in Drupal versions 10.5.12, 10.6.11, 11.2.14, and 11.3.12.
Affected products
- Drupal Drupal core <10.5.12, 10.6.x < 10.6.11, 11.0.x, 11.1.x, 11.2.x < 11.2.14, 11.3.x < 11.3.12
Timeline
- 2026-06-17: patched: Security release date for multiple branches
- 2026-07-10: disclosed: NVD publication date