CVE-2014-8169 in autofs
Summary
by MITRE
automount 5.0.8, when a program map uses certain interpreted languages, uses the calling user's USER and HOME environment variable values instead of the values for the user used to run the mapped program, which allows local users to gain privileges via a Trojan horse program in the user home directory.
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Analysis
by VulDB Data Team • 12/10/2024
The vulnerability identified as CVE-2014-8169 affects automount version 5.0.8 and represents a critical privilege escalation flaw that exploits the improper handling of environment variables during program execution. This issue specifically manifests when automount processes program maps that utilize interpreted languages such as shell scripts or Perl scripts, creating a dangerous misalignment between the executing user context and the environment variables that are utilized during program execution. The flaw stems from automount's failure to properly isolate the execution environment, instead allowing the calling user's USER and HOME environment variables to persist and influence the execution context of mapped programs, which creates a significant security boundary violation.
The technical implementation of this vulnerability relies on the improper environment variable handling within the automount daemon's execution pipeline. When a user accesses an automounted filesystem that contains a program map using interpreted languages, the automount service executes the mapped program with the environment variables set to the values of the calling user rather than the target user whose context the program should execute under. This misconfiguration creates a scenario where a local attacker can manipulate the execution environment by placing malicious code in the user's home directory, effectively allowing the attacker to execute code with elevated privileges. The vulnerability operates at the intersection of privilege management, environment variable handling, and execution context isolation, making it particularly dangerous in multi-user environments where different users may have varying privilege levels.
The operational impact of CVE-2014-8169 extends beyond simple privilege escalation to encompass potential system compromise and unauthorized access to sensitive resources. Attackers can leverage this vulnerability to execute arbitrary code with the privileges of the target user, potentially leading to full system compromise if the target user has administrative privileges. The attack vector requires local access and relies on the presence of automounted filesystems with interpreted language program maps, making it more prevalent in environments where automount is actively used for network filesystem mounting. This vulnerability directly maps to CWE-276, which addresses improper privileges, and aligns with ATT&CK technique T1068, which involves exploiting local privileges to escalate access. The flaw essentially creates a Trojan horse scenario where malicious code in the user's home directory can be executed with elevated privileges due to the improper environment variable propagation.
Mitigation strategies for this vulnerability require immediate patching of the automount service to version 5.0.9 or later, which contains the necessary fixes for proper environment variable handling and execution context isolation. System administrators should also implement strict monitoring of automount configurations and ensure that program maps using interpreted languages are properly secured. Additional protective measures include disabling unnecessary automount functionality, implementing proper file permissions on user home directories, and regularly auditing automount configurations for potential security issues. The vulnerability demonstrates the critical importance of proper environment variable isolation in privilege escalation scenarios and highlights the need for security-conscious development practices that consider the full execution context of automated services. Organizations should also implement principle of least privilege practices and regularly test their systems against known vulnerabilities to prevent exploitation of similar issues in other services.