CVE-2018-18629 in Command Line Client
Summary
by MITRE
An issue was discovered in the Keybase command-line client before 2.8.0-20181023124437 for Linux. An untrusted search path vulnerability in the keybase-redirector application allows a local, unprivileged user on Linux to gain root privileges via a Trojan horse binary.
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Analysis
by VulDB Data Team • 12/04/2024
The vulnerability identified as CVE-2018-18629 represents a critical privilege escalation flaw within the Keybase command-line client for Linux systems. This issue affects versions prior to 2.8.0-20181023124437 and stems from an insecure search path implementation in the keybase-redirector application. The flaw enables local unprivileged users to execute arbitrary code with elevated privileges, potentially compromising the entire system. The vulnerability manifests through a Trojan horse binary attack vector that exploits the client's failure to properly validate executable paths during the redirection process.
The technical root cause of this vulnerability aligns with CWE-426, which describes the insecure use of system search paths, and CWE-276, which addresses incorrect permissions for critical resources. The keybase-redirector application fails to properly sanitize or validate the PATH environment variable, allowing an attacker to place a malicious binary with the same name as a legitimate system utility in a directory that appears earlier in the search path. When the application executes, it inadvertently runs the attacker-controlled binary instead of the intended system utility, leading to privilege escalation. This flaw operates under the principle that applications should not trust the contents of the PATH variable without proper validation.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise. An attacker with local access can leverage this vulnerability to execute commands as the root user, potentially gaining access to all system resources, sensitive data, and cryptographic keys stored within the Keybase client. The attack requires only local user privileges and does not necessitate network access or complex exploitation techniques, making it particularly dangerous in environments where local system access is not strictly controlled. The vulnerability affects all Linux distributions running vulnerable versions of the Keybase client and can be exploited across different system architectures.
Mitigation strategies for CVE-2018-18629 primarily focus on updating to the patched version of the Keybase client, specifically version 2.8.0-20181023124437 or later. Organizations should implement immediate patch management procedures to ensure all affected systems are updated. Additional defensive measures include hardening the PATH environment variable by explicitly defining system directories and removing unnecessary entries, implementing proper file permissions for system directories, and monitoring for unauthorized modifications to critical system paths. The vulnerability also highlights the importance of following the principle of least privilege and implementing robust application sandboxing techniques. From an attack detection perspective, security monitoring should include unusual execution patterns of system utilities and unexpected privilege escalation events. This vulnerability demonstrates the critical importance of secure coding practices and proper input validation, particularly when dealing with system-level operations and environment variable handling. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically using insecure search paths as a method to gain elevated system access.