CVE-2026-57645: Newsletters Auth Bypass Vulnerability

CVE-2026-57645 Overview

CVE-2026-57645 is a broken access control vulnerability in the WordPress Newsletters plugin affecting versions up to and including 4.13. The flaw resides in the newsletters_subscribers functionality and stems from missing authorization checks [CWE-862]. Attackers can exploit this issue remotely over the network with low complexity and no prior authentication, though user interaction is required. Successful exploitation impacts integrity and availability of subscriber data managed by the plugin.

Critical Impact
An unauthenticated attacker can manipulate subscriber records and disrupt newsletter operations on affected WordPress sites, provided a user is tricked into interacting with a crafted request.

Affected Products

WordPress Newsletters plugin (newsletters-lite) versions <= 4.13

Discovery Timeline

2026-06-26 - CVE-2026-57645 published to NVD
2026-06-26 - Last updated in NVD database

Technical Details for CVE-2026-57645

Vulnerability Analysis

The Newsletters plugin exposes functionality tied to the newsletters_subscribers component without enforcing proper authorization. This class of flaw, categorized as Missing Authorization [CWE-862], allows requests to reach sensitive operations that should be restricted to authenticated administrators. Because the plugin does not verify the caller's privileges before executing subscriber-related actions, an attacker can trigger operations that modify or destroy subscriber records.

The issue affects all versions of the plugin up to and including 4.13. The EPSS probability is currently 0.189%, indicating limited observed exploitation activity, but the network-accessible nature of the flaw raises exposure across any WordPress site running a vulnerable version.

Root Cause

The root cause is the absence of capability or nonce validation on request handlers that manage newsletter subscribers. WordPress plugins are expected to gate privileged actions with functions such as current_user_can() and check_admin_referer(). The vulnerable handlers omit these checks, allowing the plugin to execute state-changing operations on behalf of any requester who reaches the endpoint.

Attack Vector

Exploitation occurs over the network and requires user interaction, typically by luring an authenticated site user or administrator to a crafted page or link. Once the victim's browser issues the request, the plugin processes the action without verifying that the caller is authorized. The impact focuses on integrity and availability, enabling subscriber data tampering or removal without directly exposing confidential data. For technical specifics, refer to the Patchstack WordPress Vulnerability Report.

Detection Methods for CVE-2026-57645

Indicators of Compromise

Unexpected modifications or deletions in the WordPress wp_newsletters_* database tables.
HTTP requests to Newsletters plugin endpoints referencing newsletters_subscribers originating from unauthenticated sessions.
Subscriber list changes not correlated with legitimate administrator activity in the WordPress audit log.

Detection Strategies

Review web server access logs for POST or GET requests targeting Newsletters plugin routes without a valid authenticated session cookie.
Enable and monitor WordPress activity logging plugins to capture subscriber-related state changes and correlate them with admin sessions.
Compare installed plugin versions against 4.13 or lower across managed WordPress deployments using inventory tooling.

Monitoring Recommendations

Alert on anomalous request volumes to wp-admin/admin-ajax.php or wp-admin/admin-post.php with action parameters tied to the Newsletters plugin.
Track referrer headers and user agents on newsletter management endpoints to detect cross-site request patterns.
Ingest WordPress and web server logs into a centralized analytics platform to baseline normal subscriber management behavior.

How to Mitigate CVE-2026-57645

Immediate Actions Required

Update the Newsletters plugin to a version later than 4.13 as soon as a fixed release is available from the vendor.
Audit existing subscriber tables and administrative activity logs for unauthorized changes.
Restrict access to WordPress administrative endpoints using web application firewall rules or IP allowlisting.

Patch Information

Refer to the Patchstack WordPress Vulnerability Report for the latest fixed version guidance. Apply the vendor-supplied update through the WordPress plugin manager or by deploying the patched release through configuration management tooling.

Workarounds

Deactivate the Newsletters plugin until a patched version is installed if newsletter functionality is not business critical.
Deploy a web application firewall rule blocking unauthenticated requests to Newsletters plugin endpoints.
Enforce strong administrator session hygiene, including short session lifetimes and mandatory logout, to reduce user-interaction-based exploitation windows.

bash

# Configuration example: block unauthenticated access to Newsletters plugin endpoints via nginx
location ~* /wp-admin/admin-(ajax|post)\.php {
    if ($arg_action ~* "^newsletters_") {
        set $block_flag 1;
    }
    if ($http_cookie !~* "wordpress_logged_in_") {
        set $block_flag "${block_flag}1";
    }
    if ($block_flag = "11") {
        return 403;
    }
}