CVE-2026-1490 in Spam protection, Anti-Spam, FireWall Plugin
Summary
by MITRE • 02/15/2026
The Spam protection, Anti-Spam, FireWall by CleanTalk plugin for WordPress is vulnerable to unauthorized Arbitrary Plugin Installation due to an authorization bypass via reverse DNS (PTR record) spoofing on the 'checkWithoutToken' function in all versions up to, and including, 6.71. This makes it possible for unauthenticated attackers to install and activate arbitrary plugins which can be leveraged to achieve remote code execution if another vulnerable plugin is installed and activated. Note: This is only exploitable on sites with an invalid API key.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/20/2026
The vulnerability identified as CVE-2026-1490 affects the Spam protection, Anti-Spam, FireWall by CleanTalk plugin for WordPress, presenting a critical authorization bypass flaw that undermines the security posture of affected systems. This vulnerability resides within the 'checkWithoutToken' function and impacts all plugin versions up to and including 6.71, creating a pathway for unauthenticated attackers to escalate their privileges and gain unauthorized access to plugin installation capabilities. The exploitation mechanism leverages reverse dns spoofing through PTR record manipulation, a technique that demonstrates sophisticated understanding of network layer vulnerabilities and how they can be abused within application contexts.
The technical implementation of this vulnerability exploits the plugin's trust mechanism based on reverse DNS lookups, where the system incorrectly validates incoming requests by relying on potentially spoofable PTR record information rather than implementing proper authentication checks. This authorization bypass allows attackers to circumvent the standard WordPress authentication flow and directly access plugin installation endpoints. The vulnerability's severity is amplified by its requirement for an invalid API key, suggesting that the plugin's security model becomes fundamentally compromised when proper API validation fails, creating a dangerous state where attackers can leverage the system's inherent trust assumptions against it.
The operational impact of this vulnerability extends beyond simple unauthorized plugin installation, as it creates a potential pathway for remote code execution when combined with other vulnerable plugins on the same system. This represents a classic privilege escalation scenario where an initial foothold through unauthorized plugin installation can be leveraged to achieve complete system compromise. Attackers can install malicious plugins that may contain backdoors, web shells, or other malicious code that can be executed with the privileges of the web server, potentially leading to data theft, service disruption, or further lateral movement within the network infrastructure. The combination of this vulnerability with the requirement for an invalid API key creates a specific exploitation scenario that attackers must carefully orchestrate to maximize their impact.
Security professionals should recognize this vulnerability as a manifestation of CWE-284, which addresses improper access control in software systems, and it aligns with ATT&CK technique T1190, which covers exploitation of remote services through the use of valid credentials or by bypassing authentication mechanisms. The vulnerability demonstrates how network-level trust assumptions can be exploited to undermine application-level security controls, highlighting the importance of implementing defense-in-depth strategies that do not rely solely on network-level validations. Organizations should implement immediate mitigations including plugin version updates, proper API key validation, and network-level restrictions on plugin installation endpoints, while also monitoring for unauthorized plugin installations that may indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper authentication mechanisms and the dangers of relying on potentially spoofable network-level identifiers for security decisions in web applications.