CVE-2026-4162: Gravity SMTP Auth Bypass Vulnerability

CVE-2026-4162 Overview

The Gravity SMTP plugin for WordPress is vulnerable to Missing Authorization in versions up to, and including, 2.1.4. This vulnerability exists due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with subscriber-level access and above, to uninstall and deactivate the plugin and delete plugin options. Notably, this vulnerability is also exploitable via a Cross-Site Request Forgery (CSRF) vector.

Critical Impact

Attackers with minimal subscriber-level access can disrupt email functionality by uninstalling, deactivating, or modifying the Gravity SMTP plugin configuration, potentially breaking critical email communications on affected WordPress sites.

Affected Products

• Gravity SMTP plugin for WordPress versions up to and including 2.1.4
• WordPress installations using vulnerable Gravity SMTP versions
• Sites with subscriber-level or higher authenticated users

Discovery Timeline

• 2026-04-10 - CVE CVE-2026-4162 published to NVD
• 2026-04-13 - Last updated in NVD database

Technical Details for CVE-2026-4162

Vulnerability Analysis

This vulnerability is classified as CWE-862: Missing Authorization, a configuration and design flaw where the application fails to perform authorization checks before executing privileged actions. The Gravity SMTP plugin does not properly validate whether authenticated users have sufficient permissions before allowing them to perform administrative actions such as plugin deactivation, uninstallation, and deletion of plugin options.

The attack can be executed remotely over the network without requiring user interaction. An attacker only needs subscriber-level authentication to exploit this vulnerability, which represents a low privilege requirement. While the vulnerability does not expose confidential data, it poses a significant risk to the integrity of plugin settings and a limited availability impact through service disruption.

Root Cause

The root cause of this vulnerability is the absence of proper capability checks in the plugin's administrative action handlers. WordPress provides a robust role and capability system that plugins should leverage to restrict sensitive operations to administrators. The Gravity SMTP plugin failed to implement these authorization checks, allowing any authenticated user—including those with the lowest subscriber role—to execute privileged actions that should be restricted to administrators only.

Attack Vector

The vulnerability can be exploited through two primary attack vectors:

1. Direct Exploitation: An authenticated attacker with subscriber-level access can directly invoke the vulnerable endpoints to deactivate or uninstall the plugin and delete its configuration options.

2. CSRF Attack: The vulnerability is also exploitable via Cross-Site Request Forgery. An attacker can craft a malicious page that, when visited by an authenticated WordPress user, triggers unauthorized actions against the Gravity SMTP plugin without the victim's knowledge.

The attack does not require complex conditions and can be executed with standard web requests. The impact primarily affects the integrity of the WordPress installation by allowing unauthorized modification or removal of plugin functionality.

Detection Methods for CVE-2026-4162

Indicators of Compromise

• Unexpected deactivation or removal of the Gravity SMTP plugin from WordPress installations
• Missing or corrupted Gravity SMTP plugin options in the WordPress database
• User activity logs showing subscribers or low-privilege users accessing plugin management endpoints
• Sudden email delivery failures due to SMTP plugin being disabled

Detection Strategies

• Monitor WordPress admin action logs for plugin deactivation or uninstallation events initiated by non-administrator users
• Implement file integrity monitoring to detect unexpected changes to plugin directories
• Review web server access logs for suspicious POST requests to Gravity SMTP administrative endpoints from authenticated sessions
• Deploy WordPress security plugins that track capability misuse and unauthorized privilege escalation attempts

Monitoring Recommendations

• Enable comprehensive WordPress audit logging to capture all plugin management actions with associated user context
• Configure alerts for any plugin state changes (activation, deactivation, deletion) performed by users without administrator capabilities
• Monitor for CSRF attack indicators such as cross-origin requests to administrative endpoints
• Review email delivery metrics for sudden disruptions that could indicate plugin tampering

How to Mitigate CVE-2026-4162

Immediate Actions Required

• Update Gravity SMTP plugin to version 2.1.5 or later immediately
• Audit subscriber and contributor accounts for any suspicious or unnecessary users
• Review plugin activity logs for any evidence of exploitation
• Verify Gravity SMTP plugin settings and restore from backup if tampering is detected

Patch Information

Gravity Forms has released version 2.1.5 of the Gravity SMTP plugin to address this vulnerability. The patch implements proper authorization checks to ensure that only users with appropriate administrative capabilities can perform plugin management actions. For more details, see the Gravity Forms Announcement and the Wordfence Vulnerability Report.

Workarounds

• Restrict user registration to prevent unauthorized creation of subscriber accounts that could be used to exploit the vulnerability
• Implement additional access controls at the web server level to restrict access to WordPress administrative endpoints
• Use a Web Application Firewall (WAF) to detect and block suspicious requests targeting plugin management functions
• Temporarily disable the Gravity SMTP plugin if an immediate update is not possible, switching to an alternative email solution

# Configuration example
# Verify current Gravity SMTP version via WP-CLI
wp plugin list --name=gravitysmtp --fields=name,status,version

# Update Gravity SMTP to the patched version
wp plugin update gravitysmtp

# Audit recent plugin activity (if using audit logging)
wp db query "SELECT * FROM wp_audit_log WHERE object_type='plugin' ORDER BY created_on DESC LIMIT 20;"