CVE-2026-15916: Drupal Core Authorization Bypass Vulnerability

CVE-2026-15916 Overview

CVE-2026-15916 is a Missing Authorization vulnerability [CWE-862] in Drupal core that permits forceful browsing to resources that should require authorization checks. An attacker can reach protected functionality without the access controls the application intends to enforce. Successful exploitation requires user interaction and involves high attack complexity, limiting practical exploitation scenarios. The Drupal Security Team has published fixes as part of advisory SA-Core-2026-010.

Critical Impact
Unauthenticated attackers may access or modify Drupal-managed resources bypassing intended authorization, resulting in limited confidentiality and integrity impact on affected sites.

Affected Products

Drupal core versions 0.0.0 through 10.6.13
Drupal core versions 11.3.0 through 11.3.14 and 11.4.0 through 11.4.4
Drupal core branches 11.0.*, 11.1.*, and 11.2.* (all releases)

Discovery Timeline

2026-08-25 - CVE-2026-15916 published to NVD
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-15916

Vulnerability Analysis

The vulnerability stems from Drupal core failing to enforce authorization on one or more request paths or route handlers. An attacker who knows or guesses the target URL can retrieve or interact with resources without passing the access checks the application should invoke. This class of flaw is commonly referred to as forceful browsing.

Exploitation is network-based and requires no privileges, but it does require user interaction and involves high attack complexity. Both confidentiality and integrity impact are rated low, and there is no availability impact. The EPSS probability is 0.132%, indicating a low likelihood of exploitation activity in the near term.

Root Cause

The root cause is a Missing Authorization weakness [CWE-862]. Drupal core exposes routes or resources without invoking the permission or access-check logic that gates equivalent authenticated functionality. As a result, the application relies on obscurity of the endpoint rather than enforced access control.

Attack Vector

An attacker crafts a request to a Drupal endpoint that lacks proper authorization enforcement. A victim interacting with attacker-supplied content (such as a link) triggers the request in the victim's authenticated or unauthenticated context. Because attack complexity is high, the attacker must satisfy conditions outside their direct control for the request to reach a vulnerable state. Refer to the Drupal Security Advisory SA-Core-2026-010 for endpoint-specific technical details.

No public exploit code, proof-of-concept, or CISA KEV listing exists for this CVE at publication time.

Detection Methods for CVE-2026-15916

Indicators of Compromise

Unexpected HTTP 200 responses to unauthenticated or anonymous requests against Drupal admin, configuration, or content-management routes.
Access log entries showing anonymous sessions reaching endpoints normally requiring authenticated roles.
Modifications to Drupal content, taxonomy, or configuration entities without a corresponding authenticated user session in audit logs.

Detection Strategies

Compare Drupal request logs against the site's role and permission matrix to identify anonymous access to permission-gated routes.
Deploy web application firewall rules that inspect requests to Drupal routes disclosed in SA-Core-2026-010 and alert on anonymous access.
Baseline expected request patterns per user role and flag deviations, particularly requests originating from referrers on external domains.

Monitoring Recommendations

Enable Drupal's dblog or syslog module and forward events to a centralized SIEM for correlation.
Monitor web server access logs for spikes in 404 and 403 responses that may indicate endpoint enumeration prior to a successful forceful-browsing request.
Track configuration changes and content revisions to detect unauthorized modifications resulting from bypassed authorization checks.

How to Mitigate CVE-2026-15916

Immediate Actions Required

Upgrade Drupal core to a fixed release above 10.6.13, 11.3.14, or 11.4.4 per the guidance in SA-Core-2026-010.
Retire Drupal 11.0.*, 11.1.*, and 11.2.* sites and migrate to a supported patched branch.
Review Drupal audit logs and content revisions for signs of unauthorized changes prior to patching.

Patch Information

The Drupal Security Team addressed CVE-2026-15916 in advisory Drupal Security Advisory SA-Core-2026-010. Site operators should apply the referenced core update and clear the Drupal cache after upgrading. Composer-managed sites can update using composer update drupal/core --with-dependencies and confirm the installed version with drush status.

Workarounds

Restrict access to affected Drupal routes at the reverse proxy or WAF layer until the core patch is applied.
Disable non-essential Drupal modules that expose the vulnerable functionality if identified in the advisory.
Require authenticated sessions for administrative paths using network-level controls such as IP allowlists or VPN gating.

bash

# Configuration example: update Drupal core with Composer and verify version
composer update drupal/core drupal/core-recommended drupal/core-composer-scaffold --with-all-dependencies
vendor/bin/drush updatedb -y
vendor/bin/drush cache:rebuild
vendor/bin/drush status | grep -i 'Drupal version'