CVE-2026-55808: Drupal core XSS via improper image upload validation in JSON:API and REST

CVE-2026-55808 · Severity: info · CVSS 4.2 · Published 2026-07-10

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.

Technologies: Drupal, drupal/core (Packagist). Vendors: Drupal, Packagist.

Quick answers

Is CVE-2026-55808 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55808 being exploited in the wild.
How severe is CVE-2026-55808?
Informational severity, with a CVSS score of 4.2, published 10 July 2026.
Which products and versions are affected?
Drupal <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; drupal/core (Packagist) ECOSYSTEM:introduced=0,fixed=10.5.12|ECOSYSTEM:introduced=10.6.0,fixed=10.6.11|ECOSYSTEM:introduced=11.2.0,fixed=11.2.14|ECOSYSTEM:introduced=11.3.0,fixed=11.3.12|ECOSYSTEM:introduced=11.0.0,fixed=11.1.0|ECOSYSTEM:introduced=11.1.0,fixed=11.2.0.
Is there a fix for CVE-2026-55808?
Yes. drupal/core (Packagist): upgrade to 10.5.12 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55808 attacked?
It is attacked over the network, in a web application.
Am I affected by CVE-2026-55808?
Check whether you run Drupal or drupal/core (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • drupal/core (Packagist): upgrade to 10.5.12 or later
    composer require drupal/core:^10.5.12

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

Identifiers

  • CVE-2026-55808
  • DRUPAL-CORE-2026-009

Timeline

  • 2026-06-17: patched: Security release date for multiple branches
  • 2026-07-10: disclosed: NVD publication date

References

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