CVE-2026-2831: MailArchiver WordPress Plugin SQLi Flaw

CVE-2026-2831 Overview

The MailArchiver plugin for WordPress contains a SQL Injection vulnerability in the logid parameter affecting all versions up to and including 4.5.0. The vulnerability stems from insufficient escaping on user-supplied input and inadequate preparation of existing SQL queries. Authenticated attackers with Administrator-level access or above can exploit this flaw to append malicious SQL queries, potentially extracting sensitive information from the WordPress database.

Critical Impact

Authenticated attackers with administrative privileges can extract sensitive database information through SQL injection in the MailArchiver plugin's log viewing functionality.

Affected Products

• MailArchiver Plugin for WordPress versions up to and including 4.5.0

Discovery Timeline

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

Technical Details for CVE-2026-2831

Vulnerability Analysis

This SQL Injection vulnerability (CWE-89) exists in the MailArchiver plugin's event handling functionality. The flaw is located in the logid parameter processing, where user input is incorporated into SQL queries without proper sanitization or parameterized query implementation. While the vulnerability requires Administrator-level authentication, successful exploitation allows attackers to manipulate database queries and extract sensitive information that should not be accessible through normal application functionality.

The vulnerable code paths can be found in the class-events.php and class-eventviewer.php files within the plugin. These components handle log event retrieval and display functionality where the logid parameter is processed.

Root Cause

The root cause of this vulnerability is improper input validation and the failure to use WordPress's prepared statement functionality ($wpdb->prepare()) when constructing SQL queries that incorporate user-supplied data. The logid parameter is directly concatenated or insufficiently escaped before being included in database queries, allowing SQL injection payloads to be executed.

Attack Vector

The attack vector is network-based and requires an authenticated session with Administrator-level privileges or higher. An attacker with valid administrative credentials can craft malicious requests containing SQL injection payloads in the logid parameter. When the application processes these requests through the event viewer functionality, the injected SQL commands are executed against the database, enabling data extraction.

The vulnerability manifests in the log viewing functionality of the MailArchiver plugin. When an administrator views mail archive events, the logid parameter is processed to retrieve specific log entries. Due to insufficient input sanitization, an attacker can inject additional SQL clauses to extract data beyond the intended query scope. For detailed technical analysis, see the Wordfence Vulnerability Analysis.

Detection Methods for CVE-2026-2831

Indicators of Compromise

• Unusual SQL error messages in WordPress error logs related to MailArchiver plugin operations
• Abnormal administrator activity patterns, particularly around mail archive log viewing functions
• Database queries containing SQL injection patterns such as UNION SELECT, OR 1=1, or time-based payloads in requests to MailArchiver endpoints
• Unexpected access to sensitive database tables not normally accessed by the MailArchiver plugin

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block SQL injection patterns in WordPress admin requests
• Monitor WordPress admin panel access logs for suspicious logid parameter values containing SQL syntax
• Deploy SentinelOne Singularity to detect anomalous database query patterns and potential data exfiltration attempts
• Enable WordPress database query logging and establish baselines for normal MailArchiver plugin behavior

Monitoring Recommendations

• Enable detailed logging for WordPress administrative actions, particularly for MailArchiver plugin interactions
• Set up alerts for SQL injection signature patterns in HTTP request logs targeting /wp-admin/ paths
• Monitor database access patterns for queries originating from the MailArchiver plugin that access unexpected tables

How to Mitigate CVE-2026-2831

Immediate Actions Required

• Update the MailArchiver plugin to the latest version that addresses this vulnerability
• Audit administrator accounts to ensure only trusted users have administrative access
• Review WordPress database for signs of unauthorized data access or extraction
• Consider temporarily disabling the MailArchiver plugin until a patched version can be applied

Patch Information

Users should update the MailArchiver plugin to a version newer than 4.5.0 when available from the WordPress plugin repository. Monitor the official WordPress plugin page and the Wordfence vulnerability disclosure for patch availability announcements.

Workarounds

• Restrict administrative access to trusted IP addresses only using WordPress security plugins or server-level configuration
• Implement additional WAF rules to filter SQL injection patterns in requests to WordPress admin endpoints
• Temporarily disable the MailArchiver plugin if mail archiving functionality is not critical to operations
• Enable WordPress audit logging to track all administrative actions for forensic purposes

# Example: Restrict WordPress admin access by IP in .htaccess
# Add to /wp-admin/.htaccess
<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.100$
  RewriteCond %{REMOTE_ADDR} !^10\.0\.0\.50$
  RewriteRule .* - [F,L]
</IfModule>