CVE-2026-15087: Drupal Clean RESTful Auth Bypass Flaw

CVE-2026-15087 Overview

CVE-2026-15087 is an improper authentication vulnerability [CWE-287] affecting the Drupal Clean RESTful contributed module. The flaw allows an authenticated attacker with high privileges to compromise confidentiality and integrity of data exposed through the module's REST endpoints. Exploitation occurs over the network without user interaction, though the attack complexity is high. The issue is documented in the Drupal Security Advisory.

Critical Impact
Authenticated attackers can bypass authentication checks in the Clean RESTful module to access or modify data intended for other users through Drupal's REST API surface.

Affected Products

Drupal Clean RESTful contributed module
Drupal sites exposing REST endpoints through the Clean RESTful module
Web applications relying on Clean RESTful for API authentication

Discovery Timeline

2026-07-10 - CVE CVE-2026-15087 published to NVD
2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-15087

Vulnerability Analysis

The Clean RESTful module extends Drupal's REST capabilities to provide cleaner API endpoints for consuming content and resources. The vulnerability resides in the module's authentication layer, which fails to properly validate the identity or authorization context of requests reaching protected endpoints. An attacker holding valid but limited credentials can leverage this weakness to interact with resources beyond their intended scope.

Because the flaw involves authentication logic rather than input handling, standard input validation controls do not mitigate the issue. The Drupal advisory categorizes the weakness under CWE-287, indicating that the identity verification step can be bypassed under specific conditions. Exploitation requires network access to the Drupal site's REST interface and existing privileged credentials.

Root Cause

The root cause is improper authentication enforcement within the Clean RESTful module's request handling pipeline. The module accepts requests without fully verifying that the caller is authorized for the requested operation, breaking the trust boundary between authenticated sessions and endpoint-level authorization.

Attack Vector

The attack originates over the network against the Drupal site's REST API. An attacker with valid high-privilege credentials sends crafted requests to endpoints exposed by the Clean RESTful module. Successful exploitation results in unauthorized read and write access to protected resources. Confidentiality and integrity are impacted; availability is not affected. No public proof-of-concept exploit is currently available.

The vulnerability manifests in the module's authentication resolver. See the Drupal advisory for technical remediation details.

Detection Methods for CVE-2026-15087

Indicators of Compromise

Unexpected REST API requests to Clean RESTful endpoints from authenticated user accounts accessing resources outside their normal scope.
Anomalous read or write operations logged in Drupal's watchdog table against content owned by other users.
Repeated 200-status responses on endpoints that should return 401 or 403 for the requesting session.

Detection Strategies

Enable verbose logging for the Clean RESTful module and correlate request identities against the resources returned.
Deploy Web Application Firewall (WAF) rules that baseline REST endpoint access per role and flag deviations.
Review Drupal audit logs for privilege changes or unusual API activity following the vulnerability disclosure date.

Monitoring Recommendations

Forward Drupal access and watchdog logs to a centralized SIEM for cross-account correlation.
Alert on authenticated sessions accessing REST endpoints they have not historically used.
Track outbound data volume from REST endpoints to identify potential bulk extraction.

How to Mitigate CVE-2026-15087

Immediate Actions Required

Apply the patched version of the Clean RESTful module referenced in the Drupal Security Advisory.
Audit user accounts with elevated Drupal permissions and rotate credentials for any suspected of compromise.
Review REST endpoint exposure and restrict access to trusted networks where practical.

Patch Information

Drupal has published remediation guidance in advisory sa-contrib-2026-078. Site administrators should update the Clean RESTful module to the fixed release identified in that advisory and clear Drupal caches after upgrade to ensure the updated authentication logic is loaded.

Workarounds

Disable the Clean RESTful module until the patched version can be deployed if REST endpoints are not business-critical.
Restrict access to /api and Clean RESTful endpoint paths via reverse proxy or firewall rules limiting source IPs.
Reduce the number of accounts holding high-privilege roles to minimize the pool of credentials capable of triggering the flaw.

bash

# Configuration example: disable the Clean RESTful module via Drush
drush pm-uninstall clean_restful
drush cache:rebuild