CVE-2026-108121 in SME Server
Summary
by MITRE • 10/19/2026
Brian Mariani from DigitalCanion SA has discovered a vulnerability in the domain creation functionality of koozali's SME Server version 11.0rc1-215, allowing an attacker with high privileges to inject reserved Apache configuration directives, corrupting httpd.conf and preventing Apache from starting after a server reboot, resulting in a denial-of-service (DoS) condition affecting the web server and its hosted virtual hosts.
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Analysis
by VulDB Data Team • 10/19/2026
The vulnerability identified by Brian Mariani within koozali SME Server version 11.0rc1-215 represents a critical configuration management flaw located specifically in the domain creation functionality of the system. This software, which serves as an integrated server solution for small to medium enterprises, relies heavily on automated scripts and templates to manage Apache HTTP server configurations. The core technical issue stems from insufficient input validation and sanitization mechanisms when processing user-supplied data during the provisioning of new domains or virtual hosts. When a privileged administrator initiates the creation of a domain, the system constructs configuration directives for httpd.conf without adequately filtering out reserved keywords or structural elements that are intended to be managed exclusively by the server's internal logic. This lack of strict boundary enforcement allows an attacker with high privileges, such as a compromised administrative account, to inject arbitrary Apache configuration directives into the generated configuration file.
From a technical perspective, this flaw is classified under CWE-94 Improper Control of Generation of Code or Script, specifically involving code injection through misconfigured parameters. The vulnerability exploits the trust relationship between the application layer and the underlying web server daemon. By injecting reserved directives that conflict with existing configurations or are syntactically invalid in certain contexts, the attacker causes a corruption of the httpd.conf file. This corruption is not merely cosmetic; it fundamentally breaks the syntax parsing logic required by Apache to initialize its modules and load virtual host definitions. Consequently, when the server undergoes a reboot or when the Apache service is restarted manually, the daemon fails to start because it encounters fatal errors during configuration loading. The system effectively becomes unable to serve web content until the corrupted configuration file is manually corrected by an administrator with access to the command line interface.
The operational impact of this vulnerability is severe, resulting in a denial-of-service condition for all web services hosted on the affected SME Server. Since Apache serves as the primary front-end for most enterprise applications managed by koozali's solution, its failure renders all associated virtual hosts inaccessible to end-users. This disruption affects business continuity, potentially halting e-commerce operations, internal portals, and other critical web-based workflows dependent on the server. The severity is compounded by the fact that exploitation requires high privileges, meaning it typically stems from insider threats or compromised administrative credentials rather than remote unauthenticated attacks. However, in environments where privilege escalation has occurred via other vectors, this vulnerability provides a reliable method to disrupt service availability without needing further complex exploits.
In terms of threat modeling and industry standards, this incident aligns with MITRE ATT&CK technique T1562 Impair Defenses, specifically the sub-technique T1562.001 Disable or Modify Tools, as it involves modifying system configuration files to impair the functionality of security-critical services like web servers. It also relates to T1496 Resource Hijacking if the resulting instability leads to resource exhaustion during failed restart attempts. The vulnerability highlights a broader class of issues in server management software where automated configuration generation lacks robust validation against reserved keywords and structural integrity checks.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Administrators should immediately audit httpd.conf files for any injected directives, particularly those introduced during recent domain creation activities. If the service is currently down due to a reboot or restart, manual intervention is required to restore valid configuration syntax before Apache can be brought back online. To prevent recurrence, koozali and similar vendors must implement strict allow-listing of permitted configuration parameters for user-defined domains. Input validation routines should explicitly reject any attempts to inject reserved directives such as ServerName, DocumentRoot, or other structural tags that are managed by the system core. Additionally, implementing a staging environment where configuration changes are validated before being applied to production can catch syntax errors and injection attempts early in the deployment pipeline. Regular security audits of server management scripts and adherence to secure coding practices for configuration file generation are essential to maintaining the integrity and availability of web services on these platforms.