CVE-2011-4578 in acpid2
Summary
by MITRE
event.c in acpid (aka acpid2) before 2.0.11 does not have an appropriate umask setting during execution of event-handler scripts, which might allow local users to (1) perform write operations within directories created by a script, or (2) read files created by a script, via standard filesystem system calls.
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Analysis
by VulDB Data Team • 12/12/2021
The vulnerability identified as CVE-2011-4578 affects the acpid daemon, also known as acpid2, which is responsible for handling ACPI (Advanced Configuration and Power Interface) events on Linux systems. This daemon operates with elevated privileges to manage power management events and system configuration changes, making it a critical component in the system's security architecture. The flaw resides in the event.c file within the acpid implementation, specifically concerning how the daemon manages file permissions when executing event handler scripts.
The technical root cause of this vulnerability stems from improper umask configuration during the execution of event handler scripts. Umask values control the default permissions for newly created files and directories, and when set incorrectly, they can inadvertently grant excessive privileges to local users. In this case, the acpid daemon fails to establish an appropriate umask setting before executing scripts, allowing attackers to manipulate the filesystem permissions in ways that were not intended by the system's security model. This misconfiguration creates a privilege escalation vector where local users can manipulate files and directories created by the daemon's scripts.
The operational impact of this vulnerability manifests in two primary ways that directly compromise system security. First, local users can perform write operations within directories that are created by event handler scripts, potentially allowing them to modify critical system files or inject malicious code into the system's power management infrastructure. Second, attackers can read files that are created by these scripts, which may contain sensitive information such as system configuration details, user credentials, or other confidential data that should remain protected. This dual nature of the vulnerability means that an attacker can both read and write to areas of the filesystem that should be restricted, creating a significant security risk for systems running vulnerable versions of acpid.
From a cybersecurity perspective, this vulnerability aligns with CWE-276, which describes improper file permissions, and represents a classic case of privilege escalation through improper access control mechanisms. The ATT&CK framework categorizes this under privilege escalation techniques, specifically focusing on permissions and access control mechanisms. The vulnerability demonstrates how seemingly minor configuration issues in system daemons can create substantial security implications, as the acpid service operates with elevated privileges while failing to maintain proper security boundaries during script execution. Organizations using affected versions of acpid should immediately implement mitigations including upgrading to version 2.0.11 or later, which contains the necessary fixes to properly configure umask settings. Additionally, system administrators should conduct thorough security audits of all running services to identify similar improper umask configurations that could create analogous vulnerabilities. The fix implemented in version 2.0.11 ensures that appropriate umask values are set before script execution, thereby preventing local users from gaining unauthorized access to files and directories created during event handling operations.