Drupal core - Moderately critical - Improper validation - SA-CORE-2026-009

Project: Drupal core Date: 2026-June-17 Security risk: Moderately critical 11 ∕ 25 AC:Complex/A:User/CI:Some/II:Some/E:Theoretical/TD:Uncommon Vulnerability: Improper validation Affected versions: <10.5.12 || >=10.6.0 <10.6.11 || >=11.2.0 <11.2.14 || >=11.3.0 <11.3.12 || 11.0.* || 11.1.* CVE IDs: CVE-2026-55808 Description: The JSON:API and REST modules allow you to upload image files to image fields. The validation rules check the file extension of the uploaded file but not the file MIME type. This may allow a malicious user to upload a file that is not an image. Certain web-server configurations may serve the uploaded file with its actual MIME type rather than an image type. This may lead to cross-site scripting (XSS) or other unexpected behavior. Solution: Install the latest version: Drupal 11 If you use Drupal 11.3.x, update to Drupal 11.3.12 . If you use Drupal 11.2.x, update to Drupal 11.2.14 . Drupal 10 If you use Drupal 10.6.x, update to Drupal 10.6.11 . If you use Drupal 10.5.x, update to Drupal 10.5.12 . Drupal 11.1.x, Drupal 11.0.x, Drupal 10.4.x, and below are end-of-life and do not receive security coverage. ( Drupal 8 and Drupal 9 have both reached end-of-life.) Reported By: cantina_security Fixed By: Björn Brala (bbrala) Kim Pepper (kim.pepper) Lee Rowlands (larowlan) of the Drupal Security Team Coordinated By: Damien McKenna (damienmckenna) of the Drupal Security Team Greg Knaddison (greggles) of the Drupal Security Team Lee Rowlands (larowlan) of the Drupal Security Team Dave Long (longwave) of the Drupal Security Team Juraj Nemec (poker10) of the Drupal Security Team Jess (xjm) of the Drupal Security Team