CVE-2026-15087

Executive Summary

CVE-2026-15087 is a vulnerability reported in the Drupal Clean RESTful module. The official description is minimal, stating only that the issue affects all versions of Clean RESTful. No CVSS score, CWE, or detailed technical information has been published. The EPSS score is 0.0%, indicating no active exploitation has been observed in the wild. No public proof-of-concept (PoC) code, exploit, or patch details are available at this time. This report provides a framework for analysis and detection based on the limited information, treating the vulnerability as a potential security flaw in a Drupal RESTful API module.

Supply Chain & Package Security

This vulnerability affects a Drupal module (Clean RESTful). Drupal modules are distributed via the Drupal.org project page and can be installed via Composer. The lack of patch information and the generic description suggest the vendor may not have released a fix, or the CVE is still under analysis. Organizations using this module should monitor the Drupal security advisory page for updates and consider disabling the module if it is not critical.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unassigned)
• CVSS Vector: UNKNOWN
• Attack Vector (AV): Unknown
• Attack Complexity (AC): Unknown
• Privileges Required (PR): Unknown
• User Interaction (UI): Unknown
• Scope (S): Unknown
• Confidentiality (C): Unknown
• Integrity (I): Unknown
• Availability (A): Unknown

Threat Level: Unknown. Without a CVSS score or detailed description, the severity cannot be determined. However, vulnerabilities in RESTful API modules often involve improper access control, injection, or data exposure, which could be critical.

Deep Dive & Mechanics

Due to the lack of technical details, the exact mechanics of CVE-2026-15087 are unknown. Based on the module name "Clean RESTful," it likely provides a cleaner or simplified RESTful API for Drupal. Common vulnerability classes in such modules include:

• Authentication/Authorization Bypass: Improper checks allowing unauthenticated access to sensitive endpoints.
• Insecure Direct Object Reference (IDOR): Exposing internal object IDs without proper access control.
• SQL Injection: Unsanitized input in API parameters.
• Cross-Site Scripting (XSS): Reflected or stored XSS via API responses.
• Information Disclosure: Leaking sensitive configuration or user data.

The vulnerability could affect any version of the module, as indicated by the "." version range.

Vulnerable vs. Patched Code

No patch or code comparison is available. The following is a hypothetical example of a vulnerable REST endpoint and a patched version.

Vulnerable Code (hypothetical):

// Vulnerable: No access check
function clean_restful_get_user($uid) {
  $user = user_load($uid);
  return new JsonResponse($user);
}

Patched Code (hypothetical):

// Patched: Access check added
function clean_restful_get_user($uid) {
  if (!\Drupal::currentUser()->hasPermission('access user profiles')) {
    throw new AccessDeniedHttpException();
  }
  $user = user_load($uid);
  return new JsonResponse($user);
}

Exploitation & Lab Setup

Red Team

Since no public exploit exists, a red team would need to perform manual analysis. Setup a Drupal instance with the Clean RESTful module installed. Use tools like Burp Suite or Postman to probe API endpoints for common vulnerabilities:

1. Identify Endpoints: Review the module's code or documentation to find exposed routes.
2. Test Authentication: Attempt to access endpoints without authentication.
3. Fuzz Parameters: Use a fuzzer to test for injection flaws.
4. Check for IDOR: Try accessing resources belonging to other users.

Example curl command to test an endpoint:

curl -X GET "http://target.com/api/clean-restful/user/1" -H "Accept: application/json"

Blue Team

1. Monitor API Access Logs: Look for unusual patterns, such as repeated access to the same endpoint from different IPs.
2. Enable Drupal's built-in logging: Review watchdog logs for errors related to the Clean RESTful module.
3. Use a Web Application Firewall (WAF): Create rules to block suspicious API requests.
4. Disable the module: If not required, disable Clean RESTful immediately.

Indicators of Compromise (IOCs)

• Network: Unusual HTTP requests to /api/clean-restful/* endpoints.
• Logs: Drupal watchdog entries with module name "clean_restful" and error messages.
• File System: Modified or new files in the modules/contrib/clean_restful directory.
• Database: Suspicious entries in the users or sessions tables.

Detection Engineering

YARA Rule

rule Detect_Clean_RESTful_Exploit {
    meta:
        description = "Detects potential exploitation of CVE-2026-15087 in Drupal Clean RESTful"
        author = "Valters IT"
        date = "2025-04-10"
        hash = "unknown"
    strings:
        $s1 = "clean_restful" nocase
        $s2 = "api/clean-restful" nocase
        $s3 = "Drupal\\clean_restful" nocase
    condition:
        any of them
}

Sigma Rule

title: Potential CVE-2026-15087 Exploitation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests targeting Drupal Clean RESTful endpoints
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem|contains: '/api/clean-restful/'
    condition: selection
falsepositives:
    - Legitimate API usage
level: high

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"Potential CVE-2026-15087 Exploitation - Drupal Clean RESTful";
    flow:to_server,established;
    content:"/api/clean-restful/"; http_uri;
    classtype:attempted-recon;
    sid:10000001;
    rev:1;
)

Remediation & Mitigation

1. Immediate Action: Disable the Clean RESTful module if it is not essential.
2. Monitor: Watch for updates from the Drupal security team or the module maintainer.
3. Patch: Apply any official patch as soon as it becomes available.
4. Workaround: If the module must remain enabled, restrict access to its endpoints using a web server configuration (e.g., .htaccess or Nginx rules).
5. Audit: Review all Drupal modules for similar vulnerabilities.

Example .htaccess rule to block access:

RewriteEngine On
RewriteRule ^api/clean-restful - [F,L]

Valters IT