CVE-2026-76755 in Gammu SMS Daemon Module
Summary
by MITRE • 09/02/2026
Vulnerability in Drupal Gammu SMS Daemon. This issue affects Gammu SMS Daemon versions: *.*.
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Analysis
by VulDB Data Team • 09/02/2026
The vulnerability identified within the Gammu SMS Daemon component of the Drupal ecosystem represents a significant security risk for organizations relying on automated text messaging services integrated with their content management systems. The affected software, specifically targeting all version numbers denoted as .., indicates that this flaw is pervasive across the entire release history of the module or its underlying library dependencies without specific patching measures being applied in earlier iterations. This broad scope suggests a fundamental architectural weakness rather than an edge-case logic error, potentially affecting any deployment where Gammu SMS Daemon is utilized to facilitate communication between Drupal-based applications and external telecommunication gateways. The presence of such a vulnerability underscores the critical importance of securing third-party integrations that handle sensitive user data or trigger automated actions based on system events.
At its core, this technical flaw likely stems from insufficient validation or sanitization of input parameters passed through the SMS daemon interface to the Drupal application backend. In many similar implementations involving external service daemons, attackers can exploit improperly handled command strings, message payloads, or configuration files to execute arbitrary code, manipulate database entries, or bypass authentication mechanisms. The Gammu library serves as a bridge between software applications and GSM modems, translating digital data into SMS protocols. If the daemon fails to strictly enforce type checking, length limits, or character encoding standards on incoming messages or outgoing commands, it creates an attack surface where malicious actors can inject crafted payloads. These payloads may leverage common injection techniques such as SQL injection for database manipulation or command injection for remote code execution, depending on how the underlying PHP scripts process the data received from the daemon.
The operational impact of this vulnerability is severe and multifaceted. For administrators managing Drupal sites with active SMS notification systems, an exploited flaw could lead to unauthorized access to administrative panels, leading to complete site compromise. Attackers might use the compromised system as a pivot point for further network intrusion, exfiltrate sensitive user information stored in the database via injected queries, or disrupt service availability by flooding the SMS gateway with malicious requests causing denial of service conditions. Furthermore, since SMS is often used for two-factor authentication and critical alerts, compromising this channel could undermine trust in security protocols and alert systems. The ability to manipulate outgoing messages also poses a reputational risk, as attackers could send fraudulent communications impersonating the organization, leading to phishing campaigns or social engineering attacks against customers and partners who rely on these automated notifications.
From an industry standards perspective, this vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command (OS Command Injection) if it allows remote code execution, or CWE-89 SQL Injection if the primary impact is database manipulation. It also relates to CWE-20 Improper Input Validation regarding the failure to sanitize data received from external sources. In terms of adversary tactics, this flaw facilitates techniques described in MITRE ATT&CK such as T1190 Exploit Public-Facing Application for initial access and potentially T1053 Scheduled Task/Job if persistence mechanisms are established through cron jobs triggered by SMS events. Understanding these mappings helps security teams prioritize remediation efforts based on the potential for exploitation within their specific threat landscape, recognizing that public-facing applications with external integrations are high-value targets for automated scanning tools and opportunistic attackers alike.
Mitigation strategies must focus on immediate isolation and rigorous patch management. Organizations should first verify if they are running an affected version by auditing their Drupal modules list against the Gammu SMS Daemon release notes. If a patched version is available, it should be applied immediately following standard update procedures to ensure that input validation logic has been corrected at the source code level. In cases where immediate patching is not feasible due to compatibility constraints or lack of vendor updates, network-level controls become essential. Implementing strict firewall rules to restrict communication between the web server and any local GSM modem interfaces can limit exposure. Additionally, deploying a Web Application Firewall with specific rule sets designed to detect common injection patterns in POST requests related to SMS endpoints can provide an additional layer of defense. Input validation should also be reinforced at the application level by ensuring that all data received from external services is treated as untrusted and subjected to rigorous sanitization before processing. Regular security audits and penetration testing focused on third-party integrations are recommended to identify similar weaknesses in other connected components, thereby strengthening the overall resilience of the Drupal infrastructure against evolving cyber threats.