CVE-2026-77136 in Powermail
Summary
by MITRE • 08/25/2026
The extension passes the raw value of a form field configured as "This field contains the name of the sender" directly into a Fluid View as template source, without any sanitization, and renders it. An anonymous, unauthenticated user can submit Fluid template syntax in that field to execute arbitrary Fluid ViewHelpers leading to disclosure of server configuration, environment variables and application source, and potentially remote code execution. Exploitation requires only that a form field is configured as the sender_name field, a common and default-adjacent Powermail configuration. No authentication or user interaction beyond a normal form submission is required. This vulnerability is reported to be actively exploited in the wild.
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Analysis
by VulDB Data Team • 08/25/2026
The identified vulnerability represents a critical server-side template injection flaw within a popular content management system extension designed for handling web forms. The core technical deficiency lies in the insecure processing of user-supplied input, specifically where raw values from form fields designated as sender names are passed directly into a Fluid templating engine without any sanitization or validation steps. This architectural oversight allows an attacker to inject arbitrary Fluid template syntax into the application logic. Because the vulnerable field is commonly configured and often present in default installation profiles, the attack surface is significantly broadened, affecting numerous deployments that rely on standard form configurations for contact pages or data collection mechanisms.
From a technical perspective, this flaw constitutes a classic case of improper neutralization of special elements used in an output context, which aligns with CWE-94, commonly known as Code Injection via template engines. The Fluid templating engine is designed to interpret specific syntax structures and execute ViewHelpers, which are functional components that can perform various operations ranging from simple text manipulation to complex data retrieval. By injecting malicious payload strings into the sender name field, an attacker forces the application to parse these inputs as executable code rather than static text content. This bypasses standard input validation mechanisms because the system treats the form submission as a legitimate template source, thereby granting the execution context of the backend server environment to the unauthenticated user.
The operational impact of this vulnerability is severe and multifaceted. Initially, successful exploitation allows for unauthorized disclosure of sensitive internal information. Attackers can leverage specific ViewHelpers to read configuration files, extract environment variables containing database credentials or API keys, and access application source code stored on the server filesystem. This reconnaissance phase provides a comprehensive map of the target infrastructure's security posture. More critically, certain Fluid ViewHelpers possess capabilities that extend beyond data disclosure into active command execution. Depending on the specific version and available plugins, an attacker may achieve Remote Code Execution by invoking system commands or exploiting unsafe deserialization paths within the templating engine. This transforms a simple information leak into a full compromise of the underlying server infrastructure.
The exploitability profile of this vulnerability is exceptionally high due to its low barrier to entry. It requires no authentication credentials and does not demand complex user interaction beyond submitting a standard web form, which is a routine activity for legitimate users. The fact that exploitation has been reported as active in the wild indicates that automated scanning tools or opportunistic attackers are already leveraging this flaw against vulnerable instances. This real-world activity underscores the urgency of remediation, as passive exposure to public-facing forms makes these systems prime targets for widespread compromise campaigns aimed at establishing persistent backdoors or launching further attacks from within the network perimeter.
Mitigation strategies must address both immediate containment and long-term architectural improvements. Immediate action should involve applying any available patches provided by the extension maintainer that enforce strict input validation on form fields before they are passed to the templating engine. If patching is not immediately feasible, administrators can implement a temporary workaround by disabling or removing the specific field configuration that maps user input directly to template variables, or by restricting access to forms containing this vulnerability through IP whitelisting if applicable. Long-term remediation requires adopting secure coding practices such as output encoding and parameterized templates to ensure that all dynamic content is treated strictly as data rather than executable code. Additionally, organizations should conduct a thorough audit of their form configurations to identify other instances where raw user input might be interpolated into template structures without adequate sanitization layers.
This vulnerability aligns with the MITRE ATT&CK framework under techniques related to Server-Side Request Forgery and Command Injection, specifically reflecting behaviors associated with initial access through vulnerable components and subsequent execution within a server environment. The lack of authentication requirements places it firmly in the category of unauthenticated attacks that can be automated at scale. Security teams should prioritize this issue due to its high severity score potential and active exploitation status. Regular vulnerability scanning focused on form-based applications and continuous monitoring for anomalous template parsing errors will help detect attempts to exploit similar flaws across the organization's digital assets.