Overview

The SendPress Newsletters plugin for WordPress is vulnerable to a time-based SQL injection attack. This vulnerability, tracked as CVE-2026-93855, affects all versions up to and including 1.26.1.20. The flaw arises from insufficient escaping of user-supplied parameters and a lack of preparation on existing SQL queries. This makes it possible for unauthenticated attackers to append additional SQL queries to extract sensitive information from the database.

Understanding the Vulnerability / Threat

Root Cause Analysis

The root cause of this vulnerability is a design and implementation issue. Specifically, it is a time-based SQL injection vulnerability, which falls under the CWE-89 category. The vulnerability exists because the 'subscriberid' parameter is not properly escaped, and the SQL query is not sufficiently prepared. This allows an attacker to inject malicious SQL code.

Attack Surface & Vector

This vulnerability is accessible remotely and does not require authentication. The attack vector involves exploiting the 'subscriberid' parameter. The nonce gating the handler uses a hardcoded action value 'sendpress-is-awesome', which is rendered on the same public page served by the [sp-form formid="manage"] shortcode. This makes it trivial for unauthenticated visitors to obtain the nonce and effectively bypass it as an access control mechanism.

Exploitation Mechanics — Scenario Walkthrough

Scenario: Exploiting SendPress Newsletters via Time-Based SQL Injection
Initial Position: The attacker is unauthenticated and has access to the public page of a WordPress site using the SendPress Newsletters plugin.
Triggering the Flaw: The attacker crafts a malicious request to the handler with a specially designed 'subscriberid' parameter that injects SQL code. This is possible because the nonce is easily obtainable from the public page.
What Breaks: The security boundary fails because the SQL query execution is not properly filtered, allowing the injected SQL code to be executed. This can lead to the extraction of sensitive information from the database.
Attacker's Prize: The attacker can now extract sensitive information from the database, such as user credentials or other critical data.

Real-World Impact

An attacker can use this vulnerability to extract sensitive information from the database, which can lead to further exploitation, such as lateral movement within the network, data exfiltration, or even deployment of ransomware. The affected user base includes all users of the SendPress Newsletters plugin up to version 1.26.1.20.

Detection & Defense

Immediate Mitigations

Upgrade the SendPress Newsletters plugin to a version beyond 1.26.1.20. Until a patch is applied, users can consider limiting access to the affected pages or using a Web Application Firewall (WAF) to filter out malicious SQL injection attempts.

Detection Strategies

Defenders can detect exploitation attempts by monitoring for unusual SQL queries or patterns that could indicate injection attacks. Implementing a SIEM system or using log monitoring tools can help identify potential threats. MITRE ATT&CK technique T1190 (Exploit Public-Facing Application) and T1560 (Manipulate Query String) are relevant here.

Long-Term Hardening

To prevent this class of vulnerability, developers should implement prepared statements with parameterized queries for all database interactions. Regular security audits and code reviews can also help identify and mitigate potential vulnerabilities before they become issues.

Key Takeaways

  • Time-based SQL injection vulnerabilities can allow unauthenticated attackers to extract sensitive information from databases.
  • Insufficient escaping of user-supplied parameters and lack of preparation on SQL queries are common causes of SQL injection vulnerabilities.
  • Nonce values should be securely generated and validated to prevent unauthorized access.
  • Regular updates and security audits are crucial for maintaining the security of plugins and applications.

Sources

  • National Vulnerability Database (NVD) - CVE-2026-93855