CVE-2009-4235 in acpid
Summary
by MITRE
acpid 1.0.4 sets an unrestrictive umask, which might allow local users to leverage weak permissions on /var/log/acpid, and obtain sensitive information by reading this file or cause a denial of service by overwriting this file, a different vulnerability than CVE-2009-4033.
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Analysis
by VulDB Data Team • 08/28/2021
The vulnerability described in CVE-2009-4235 affects the acpid daemon version 1.0.4 which is responsible for handling ACPI events in Linux systems. This flaw represents a privilege escalation and information disclosure vulnerability that stems from improper permission handling within the system's logging mechanism. The acpid service is designed to monitor and respond to ACPI events such as power button presses, lid closures, and battery status changes, making it a critical component in system power management and event handling.
The core technical flaw resides in how acpid initializes its environment by setting an overly permissive umask value during its execution. A umask is a permission setting that determines the default access rights for newly created files and directories. When acpid sets an unrestrictive umask, it allows any local user to create files with overly broad permissions, particularly affecting the /var/log/acpid log file. This vulnerability is classified under CWE-276, which deals with improper file permissions, and represents a classic case of inadequate access control implementation. The default umask setting typically restricts file permissions to prevent unauthorized access, but in this case, the daemon fails to properly configure this security parameter.
The operational impact of this vulnerability is significant as it provides local attackers with two distinct attack vectors. First, through information disclosure, attackers can read sensitive data from the acpid log file which may contain information about system events, power management activities, or potentially other system details that could aid in further attacks. Second, the vulnerability enables denial of service conditions where malicious users can overwrite the log file with arbitrary content, potentially disrupting the normal operation of the acpid service or masking legitimate system events. This dual nature of the vulnerability makes it particularly dangerous as it can be exploited for both reconnaissance and service disruption purposes. The attack surface is widened by the fact that local users can leverage this weakness without requiring special privileges or network access.
The security implications extend beyond immediate exploitation as this vulnerability demonstrates poor security hygiene in daemon initialization processes. According to ATT&CK framework category T1068, this represents a local privilege escalation technique that could be used as a stepping stone for more sophisticated attacks. System administrators should consider implementing additional monitoring for the acpid log file and ensure that proper file permissions are maintained even when daemon processes are running with default configurations. The vulnerability also highlights the importance of proper umask management in security-sensitive applications, as outlined in various secure coding guidelines and best practices for system hardening. Organizations should verify that all system services properly initialize their security parameters and that default configurations do not introduce unnecessary access rights that could be exploited by local users. The recommended mitigation includes updating to a patched version of acpid where the umask is properly configured or manually setting restrictive umask values in the service initialization scripts to prevent unauthorized access to sensitive log files and maintain system integrity.