CVE-2009-5054 in Smarty
Summary
by MITRE
Smarty before 3.0.0 beta 4 does not consider the umask value when setting the permissions of files, which might allow attackers to bypass intended access restrictions via standard filesystem operations.
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Analysis
by VulDB Data Team • 02/08/2019
The vulnerability identified as CVE-2009-5054 affects the Smarty template engine version 3.0.0 beta 3 and earlier, representing a significant security flaw in how the system handles file permissions during template processing operations. This issue stems from the template engine's failure to properly account for the umask value when creating or modifying filesystem objects, creating a potential pathway for unauthorized access to sensitive data and system resources. The problem occurs within the context of web applications that utilize Smarty for dynamic content generation, where template files are processed and potentially cached or stored on the filesystem. When Smarty generates or updates template files, it should respect the system's umask setting which controls default file permissions, but this behavior was not properly implemented in the affected versions, leading to potentially insecure file creation practices.
The technical implementation flaw lies in Smarty's file handling mechanisms where the system does not properly apply umask restrictions when setting file permissions for template-related files. This creates a scenario where files created by the template engine inherit default permissions that may be more permissive than intended, potentially allowing unauthorized users or processes to access or modify template files that should remain restricted. The umask value typically controls which permission bits are stripped from newly created files, and when this value is ignored, the resulting file permissions may not align with the system's security policies. This vulnerability specifically impacts the file system access controls that are fundamental to maintaining data confidentiality and integrity within web applications. The flaw can be categorized under CWE-732 as improper restriction of operations within a security scope, and it represents a direct violation of the principle of least privilege in system security design.
The operational impact of this vulnerability extends beyond simple permission misconfigurations to potentially enable attackers to gain unauthorized access to sensitive application data, manipulate template files, or even execute malicious code through compromised template processing. When attackers can bypass intended access restrictions through standard filesystem operations, they may be able to modify template logic that controls application behavior, leading to potential data breaches, privilege escalation, or complete system compromise. The vulnerability is particularly dangerous in multi-user environments or shared hosting scenarios where different users or processes may have varying levels of access rights. Attackers could exploit this weakness to access template files containing sensitive information, modify application logic, or create backdoor access points through manipulated template content. This type of vulnerability aligns with ATT&CK technique T1059 for execution through template injection and T1078 for valid accounts exploitation, as it leverages legitimate filesystem operations to achieve malicious objectives.
The recommended mitigations for this vulnerability involve immediate upgrading to Smarty version 3.0.0 beta 4 or later, which contains the necessary fixes to properly implement umask handling during file operations. Organizations should also conduct comprehensive security assessments of their existing Smarty implementations to identify any potential exploitation vectors or misconfigurations that may have been enabled by this vulnerability. System administrators should review and harden file system permissions across all template directories to ensure that even if the vulnerability exists, the impact is minimized through proper access controls. Additionally, implementing proper monitoring and logging of file system operations related to template processing can help detect potential exploitation attempts. The fix implemented in the newer versions addresses the core issue by ensuring that umask values are properly respected during file creation and modification operations, thereby restoring the intended security controls that protect application data and system integrity.