CVE-2026-111829 in Mailster Plugin
Summary
by MITRE • 10/19/2026
Improper Control of Filename for Include/Require Statement in PHP Program ('PHP Remote File Inclusion') vulnerability in WP Mailster WP Mailster wp-mailster allows PHP Local File Inclusion.This issue affects WP Mailster: from n/a through 1.9.1.0.
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Analysis
by VulDB Data Team • 10/19/2026
The vulnerability identified as a PHP Remote File Inclusion flaw within the WP Mailster plugin represents a critical security deficiency in how user-supplied input is handled during file inclusion operations. Although the initial description references remote file inclusion, the specific impact noted involves Local File Inclusion (LFI), indicating that an attacker can manipulate include or require statements to load arbitrary files from the server's filesystem rather than external URLs. This type of vulnerability arises when a PHP script incorporates user-controlled data into a path without adequate sanitization or validation against directory traversal sequences such as dot-dot-slash patterns. By exploiting this flaw, malicious actors can bypass intended access controls and force the application to execute code contained within locally stored files that were not originally intended for execution by the web server.
From a technical perspective, this issue stems from improper control over filename parameters passed to PHP's include or require functions. When these functions are used with unsanitized input derived directly from HTTP requests, such as query strings or POST data, an attacker can inject path traversal characters to navigate up directory levels and access sensitive system files. This capability allows for the reading of configuration files containing database credentials, source code repositories, or other confidential information stored on the server. In more severe scenarios where file upload capabilities are present elsewhere in the application, this vulnerability could potentially be chained with an arbitrary file upload flaw to achieve Remote Code Execution (RCE), thereby granting full control over the compromised web server environment.
The operational impact of this vulnerability is significant for any organization relying on WP Mailster versions from n/a through 1.9.1.0. Unauthorized access to sensitive files can lead to data breaches, exposing customer personal information and internal business logic. Furthermore, if an attacker successfully exploits local file inclusion to read critical configuration files, they may extract database passwords or API keys, which facilitates further lateral movement within the network infrastructure. The presence of this flaw undermines the integrity and confidentiality guarantees expected from secure web applications, potentially resulting in regulatory non-compliance under standards such as GDPR or PCI DSS due to the exposure of protected data.
To mitigate this risk, immediate action is required to update WP Mailster to a patched version that addresses these input validation deficiencies. Developers should ensure that all file inclusion operations utilize allowlists for permitted files rather than relying on user-supplied paths whenever possible. If dynamic includes are necessary, strict sanitization must be applied using functions like basename() to strip directory separators and validate against known safe filenames. Additionally, implementing Web Application Firewalls (WAF) with rules specifically targeting path traversal attempts can provide an additional layer of defense during the transition period. Regular security audits and static code analysis should also be employed to detect similar patterns in other parts of the application stack before they are exploited by adversaries.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-98, which describes Improper Control of Filename for Include/Require Statement in PHP Program. It is frequently associated with ATT&CK technique T1059, specifically Command and Scripting Interpreter sub-techniques involving local file access or execution via included scripts. Understanding these mappings helps security teams prioritize remediation efforts based on established industry frameworks and threat intelligence models that track common exploitation patterns used by cybercriminals targeting WordPress ecosystems.