CVE-2026-2831: MailArchiver WordPress SQLi Vulnerability

CVE-2026-2831 Overview

CVE-2026-2831 is a SQL Injection vulnerability in the MailArchiver plugin for WordPress affecting all versions up to and including 4.5.0. The flaw resides in the handling of the logid parameter, where insufficient escaping and inadequate query preparation allow attackers to append additional SQL statements to existing queries. Exploitation requires authenticated access at the Administrator role or higher. A successful attack enables extraction of sensitive information from the WordPress database, including credentials, session data, and stored email archive content. The vulnerability is tracked under CWE-89 and is documented by Wordfence Vulnerability ID 5bc8da1b.

Critical Impact
Authenticated administrators can execute arbitrary SQL queries against the WordPress database through the logid parameter, exposing sensitive stored data.

Affected Products

MailArchiver plugin for WordPress, all versions through 4.5.0
WordPress sites with the plugin enabled and accessible to administrator accounts
Multi-author or multi-admin WordPress deployments where administrator trust is distributed

Discovery Timeline

2026-02-27 - CVE-2026-2831 published to NVD
2026-04-15 - Last updated in NVD database

Technical Details for CVE-2026-2831

Vulnerability Analysis

The MailArchiver plugin exposes administrative event log viewing functionality through the logid request parameter. The plugin reads this parameter and incorporates it into a SQL query used to fetch log entries from the database. The query construction does not apply sufficient escaping, and the existing prepared statement logic does not properly bind the user-supplied value as a parameter. As a result, attackers can break out of the intended query context and append additional SQL syntax.

This is a classic in-band SQL injection scenario in which the database engine executes attacker-controlled clauses alongside the legitimate query. Because the affected code path runs in the context of an authenticated administrator, the injected queries execute with full database privileges granted to the WordPress database user.

Root Cause

The root cause is improper neutralization of special elements in an SQL command [CWE-89]. The vulnerable code paths in class-events.php and class-eventviewer.php accept the logid value without applying wpdb::prepare() placeholders or casting to an integer before concatenation into the SQL statement.

Attack Vector

Exploitation requires an authenticated session with Administrator-level privileges. The attacker issues a request to the MailArchiver event viewer endpoint with a crafted logid value containing additional SQL syntax such as UNION SELECT clauses. The plugin concatenates the malicious value into the live query, and the database returns attacker-selected columns, including content from the wp_users table and other sensitive tables.

The network-based attack vector means the request can originate from anywhere the WordPress admin interface is reachable. Common abuse scenarios include compromise of a low-trust administrator account, insider abuse on multi-admin sites, and post-exploitation lateral movement after credential theft.

No verified proof-of-concept code has been published. The vulnerability mechanism is described in prose based on the Wordfence advisory and the linked plugin source.

Detection Methods for CVE-2026-2831

Indicators of Compromise

HTTP requests to MailArchiver admin endpoints containing SQL metacharacters in the logid parameter, such as single quotes, UNION, SELECT, --, or /* sequences.
Web server access logs showing unusually long logid values or values that are not numeric integers.
Database query logs containing UNION or subquery patterns originating from the MailArchiver plugin code paths.
Unexpected reads against wp_users, wp_usermeta, or wp_options tables correlated with MailArchiver page views.

Detection Strategies

Inspect WordPress access logs for requests to MailArchiver pages where the logid query string parameter contains non-integer characters.
Enable MySQL or MariaDB general query logging or slow query logging temporarily to identify anomalous queries referencing the MailArchiver tables.
Deploy a Web Application Firewall rule that rejects non-numeric values for the logid parameter on MailArchiver endpoints.
Correlate administrator login events with bursts of database read activity from the WordPress process.

Monitoring Recommendations

Forward WordPress access logs and database audit logs to a centralized SIEM for query pattern analysis.
Alert on any administrator session that triggers SQL syntax errors in the PHP error log, which often indicate injection probing.
Track newly created or modified administrator accounts as a downstream indicator of credential extraction following successful injection.

How to Mitigate CVE-2026-2831

Immediate Actions Required

Update the MailArchiver plugin to a version newer than 4.5.0 once the maintainer publishes a fix referenced by the Wordfence advisory.
Audit the list of WordPress administrator accounts and remove any that are unused, shared, or assigned to non-essential users.
Enforce strong, unique passwords and multi-factor authentication for all administrator accounts to raise the cost of obtaining the privilege level required for exploitation.
Review WordPress and database logs for evidence of prior exploitation, focusing on the date range from plugin installation onward.

Patch Information

The vulnerability affects all MailArchiver versions through 4.5.0. Site operators should consult the WordPress.org plugin repository and the Wordfence advisory for the fixed release. Apply the update through the WordPress admin Plugins page or via wp-cli once available.

Workarounds

Temporarily deactivate the MailArchiver plugin on production WordPress sites until a patched version is installed.
Restrict access to the WordPress admin directory using web server access controls or IP allowlists to reduce exposure of the vulnerable endpoint.
Configure a WAF rule that enforces a strict integer pattern, such as ^[0-9]+$, on the logid parameter for MailArchiver admin routes.
Rotate WordPress administrator credentials and any secrets stored in the database after patching, in case extraction occurred prior to remediation.

bash

# Example WAF / nginx rule rejecting non-numeric logid values on MailArchiver endpoints
location ~* /wp-admin/.*mailarchiver {
    if ($arg_logid !~ "^[0-9]+$") {
        return 403;
    }
}