CVE-2026-57740 Overview
CVE-2026-57740 is a missing authorization vulnerability [CWE-862] in the AcyMailing SMTP Newsletter plugin for WordPress. The flaw affects all plugin versions up to and including 10.11.1. Authenticated attackers with low-privilege accounts can exploit incorrectly configured access control checks to reach functionality that should be restricted. Successful exploitation impacts integrity and availability of the affected WordPress site.
Critical Impact
Authenticated users with minimal privileges can bypass access controls in the AcyMailing SMTP Newsletter plugin, modifying newsletter data and disrupting mailing operations.
Affected Products
- AcyMailing SMTP Newsletter plugin for WordPress
- All versions from n/a through 10.11.1
- WordPress sites using the AcyMailing Newsletter Team's plugin
Discovery Timeline
- 2026-07-13 - CVE-2026-57740 published to NVD
- 2026-07-13 - Last updated in NVD database
Technical Details for CVE-2026-57740
Vulnerability Analysis
The vulnerability originates from missing authorization checks within the AcyMailing SMTP Newsletter plugin. The plugin exposes functionality that fails to validate whether the requesting user holds the appropriate role or capability. Any authenticated user, including low-privilege subscribers, can invoke these endpoints.
The issue is categorized under Common Weakness Enumeration [CWE-862] Missing Authorization. Exploitation requires network access and low privileges but no user interaction. The attack targets integrity and availability rather than confidentiality of stored data.
Because the plugin manages newsletter delivery through SMTP, unauthorized invocation of restricted actions can disrupt mailing campaigns and modify plugin state. Attackers can leverage this access to interfere with communications sent from the affected WordPress site.
Root Cause
The root cause is incorrectly configured access control security levels within the plugin's request handlers. The plugin fails to enforce capability checks before executing sensitive actions. This design flaw allows requests from authenticated but unprivileged accounts to succeed.
Attack Vector
The attack vector is network-based. An attacker registers or authenticates as a low-privilege WordPress user, then sends crafted requests to the vulnerable plugin endpoints. The plugin processes these requests without verifying authorization. See the Patchstack AcyMailing Vulnerability Report for additional technical details.
Detection Methods for CVE-2026-57740
Indicators of Compromise
- Unexpected changes to AcyMailing newsletter configurations, templates, or subscriber lists
- Requests to AcyMailing plugin endpoints originating from low-privilege user sessions
- Anomalous outbound SMTP traffic patterns from the affected WordPress host
- Unexplained modifications to plugin database tables prefixed with acym_
Detection Strategies
- Audit WordPress access logs for POST and GET requests targeting AcyMailing plugin routes by non-administrative users
- Enable WordPress audit logging plugins to record capability checks and administrative actions
- Correlate authentication events with subsequent plugin actions to identify privilege boundary violations
Monitoring Recommendations
- Monitor wp-admin/admin-ajax.php and REST API calls referencing acymailing action parameters
- Alert on newsletter state changes performed by users lacking editor or administrator roles
- Track plugin version inventory across managed WordPress deployments to identify vulnerable installations
How to Mitigate CVE-2026-57740
Immediate Actions Required
- Identify all WordPress instances running the AcyMailing SMTP Newsletter plugin version 10.11.1 or earlier
- Restrict new user registration on affected sites until patching is complete
- Review existing low-privilege accounts for suspicious activity and disable unused accounts
- Deploy a web application firewall rule to block anomalous requests to AcyMailing endpoints
Patch Information
At time of publication, refer to the Patchstack AcyMailing Vulnerability Report for the current patched version. Upgrade to the vendor-supplied fixed release once available.
Workarounds
- Temporarily deactivate the AcyMailing SMTP Newsletter plugin until an updated version is installed
- Enforce strict role-based access control and remove unnecessary subscriber-level accounts
- Apply WAF rules to block unauthorized requests to plugin action handlers
- Isolate the WordPress host and restrict outbound SMTP traffic to approved relays
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
