CVE-2026-90964 in Essential Real Estate Plugin
Summary
by MITRE • 11/05/2026
The Essential Real Estate WordPress plugin before 5.3.5 does not restrict the recipient of one of its contact email actions, allowing unauthenticated users to send emails to arbitrary addresses with an attacker-controlled sender header and message body through the site.
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Analysis
by VulDB Data Team • 11/05/2026
The vulnerability identified in versions of the Essential Real Estate WordPress plugin prior to 5.3.5 represents a critical failure in input validation and access control mechanisms within its email handling functionality. This flaw specifically affects one of the contact form actions, where the system fails to enforce strict restrictions on the recipient field during the email dispatch process. As a result, an unauthenticated attacker can manipulate this parameter to redirect outgoing emails to arbitrary external addresses rather than limiting them to predefined internal recipients or administrative contacts. This lack of validation allows for significant abuse of the plugin's communication features, turning a standard user interaction point into a vector for malicious activity without requiring any form of authentication or prior access credentials.
From a technical perspective, this issue is classified as an email injection vulnerability, which falls under the Common Weakness Enumeration (CWE) category CWE-918: Server-Side Request Forgery (SSRF), although it more precisely aligns with CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component. The core technical flaw lies in the insufficient sanitization and validation of user-supplied data before it is passed to PHP's mail function or similar email sending libraries. By allowing arbitrary control over the recipient field, along with the sender header and message body, the application fails to implement necessary security controls such as input filtering, output encoding, or strict allow-listing of valid destination addresses. This enables an attacker to craft a request that exploits these weaknesses, effectively hijacking the web server's email capabilities for unauthorized purposes.
The operational impact of this vulnerability is multifaceted and poses significant risks to both website administrators and their users. Primarily, it facilitates spam distribution, where attackers can utilize the compromised site as a relay to send bulk unsolicited emails, potentially leading to blacklisting of the domain by major internet service providers and email reputation services. Furthermore, the ability to control the sender header allows for sophisticated phishing campaigns that appear legitimate, increasing the likelihood of successful social engineering attacks against recipients who trust the source domain. Additionally, this vulnerability can be leveraged in conjunction with other weaknesses to perform server-side reconnaissance or exfiltrate sensitive data if combined with local file inclusion vulnerabilities, although its primary utility remains in abuse as an open relay for malicious communications.
To mitigate this risk, immediate action is required by updating the Essential Real Estate plugin to version 5.3.5 or later, where these validation checks have been implemented. In cases where patching is not immediately feasible, administrators should implement server-side controls such as configuring SMTP authentication and restricting outbound email permissions through web application firewalls (WAFs). It is also advisable to review all contact form implementations for similar patterns of unvalidated input in header fields or recipient lists. Adhering to secure coding practices that emphasize strict validation against allow-lists rather than relying on blocklists can prevent recurrence of such issues across other plugins and custom code within the WordPress environment, ensuring robust protection against email-based abuse vectors.