CVE-2011-4125 in Calibre
Summary
by MITRE • 10/27/2021
A untrusted search path issue was found in Calibre at devices/linux_mount_helper.c leading to the ability of unprivileged users to execute any program as root.
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Analysis
by VulDB Data Team • 10/31/2021
The vulnerability identified as CVE-2011-4125 represents a critical privilege escalation flaw within the Calibre digital library management software, specifically within the linux_mount_helper.c component. This issue stems from an insecure handling of the system search path that allows unprivileged users to manipulate the execution environment in a manner that can lead to arbitrary code execution with root privileges. The vulnerability exists in the way the software resolves and executes external programs during device mounting operations, creating a path traversal condition that can be exploited by malicious users.
The technical root cause of this vulnerability lies in the improper handling of environment variables and executable paths within the device mounting helper functionality. When Calibre attempts to execute system commands during device mounting, it does not properly sanitize or validate the search paths used to locate executable binaries. This untrusted search path issue creates an opportunity for attackers to place malicious executables in directories that are searched before the legitimate system binaries, effectively allowing the execution of arbitrary code with elevated privileges. The flaw operates under CWE-427 which specifically addresses uncontrolled search path, and aligns with ATT&CK technique T1068 which covers privilege escalation through untrusted search paths.
The operational impact of this vulnerability is severe as it enables any local user to escalate their privileges to root level without requiring any special authentication or authorization. An attacker can exploit this by manipulating the environment variables or by placing malicious binaries in directories that are searched before system directories, causing the helper program to execute the attacker-controlled code with root privileges. This creates a persistent backdoor that can be used for further system compromise, data exfiltration, or to establish long-term access to the affected system. The vulnerability is particularly dangerous because it requires no special privileges to exploit and can be leveraged by any user with access to the system.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and secure path handling within the application. System administrators should ensure that Calibre is updated to the latest version that contains the patched code addressing the untrusted search path issue. The recommended approach involves setting restrictive permissions on the helper binaries and ensuring that the PATH environment variable does not include potentially compromised directories. Additionally, implementing proper privilege separation and using secure coding practices such as explicitly specifying full paths to executables rather than relying on the system search path can prevent exploitation. Organizations should also consider implementing monitoring and alerting for unauthorized changes to critical system directories and executables. The fix typically involves modifying the device mounting helper to use absolute paths for all external command execution and to properly validate all environment variables before use, addressing the underlying CWE-427 vulnerability through secure coding practices that align with ATT&CK mitigation strategies for privilege escalation techniques.