CVE-2026-15917: Drupal core cross-site scripting in HTMX attribute sanitization

CVE-2026-15917 · Severity: medium · CVSS 4.7 · Published 2026-08-25

Drupal core, a widely-used open-source content management platform, contains a cross-site scripting (XSS) vulnerability in how it sanitizes HTMX JavaScript library attributes. An attacker with the ability to insert HTML into site content can execute malicious JavaScript in the browsers of site visitors, potentially stealing session tokens, modifying page content, or redirecting users to malicious sites.

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

Quick answers

Is CVE-2026-15917 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-15917 being exploited in the wild.
How severe is CVE-2026-15917?
Medium severity, with a CVSS score of 4.7, published 25 August 2026.
Which products and versions are affected?
Drupal Core 11.3.0 to 11.3.14, 11.4.0 to 11.4.4, 11.2.x and earlier; drupal/core (Packagist) ECOSYSTEM:introduced=11.3.0,fixed=11.3.14|ECOSYSTEM:introduced=11.4.0,fixed=11.4.4|ECOSYSTEM:introduced=11.2.0,fixed=11.3.0.
Is there a fix for CVE-2026-15917?
Yes. drupal/core (Packagist): upgrade to 11.3.14 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-15917 attacked?
It is attacked over the network, in a web application.
Am I affected by CVE-2026-15917?
Check whether you run Drupal Core 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 11.3.14 or later
    composer require drupal/core:^11.3.14

Technical details

The vulnerability is an improper input neutralization (CWE-79) affecting Drupal core's XSS filter, which fails to sufficiently sanitize certain HTMX attributes introduced in Drupal core 11.2 and later. The attack vector is network-based and requires the attacker to have the ability to insert HTML with specific attributes into site content (e.g., through a vulnerable contributed module or privileged user account). Successful exploitation allows arbitrary JavaScript execution in visitor browsers. The vulnerability is mitigated by access controls—an attacker must first gain content insertion capabilities. Patches are available: Drupal 11.4.4, 11.3.14, and 10.6.x include hardening fixes; Drupal 11.2.x and below are end-of-life and receive no patches.

Affected products

  • Drupal Drupal core 11.3.0 to 11.3.14, 11.4.0 to 11.4.4, 11.2.x and earlier

Identifiers

  • CVE-2026-15917
  • DRUPAL-CORE-2026-011

Timeline

  • 2026-07-15: disclosed: Drupal Security Advisory SA-CORE-2026-011
  • 2026-08-25: other: CVE-2026-15917 published to NVD

References

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