CVE-1999-1434 in Linux
Summary
by MITRE
login in Slackware Linux 3.2 through 3.5 does not properly check for an error when the /etc/group file is missing, which prevents it from dropping privileges, causing it to assign root privileges to any local user who logs on to the server.
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Analysis
by VulDB Data Team • 11/01/2024
The vulnerability described in CVE-1999-1434 represents a critical privilege escalation flaw in the login service of Slackware Linux versions 3.2 through 3.5. This issue stems from improper error handling within the authentication process where the system fails to verify the existence and accessibility of the /etc/group file before attempting to drop administrative privileges. The root cause of this vulnerability aligns with CWE-252, which addresses improper checking for error conditions, specifically in the context of privilege management. When the /etc/group file is absent from the system, the login service continues execution without proper error validation, creating a dangerous state where local users can exploit this weakness to gain root access.
The technical implementation of this flaw occurs during the login process when the system attempts to establish user groups and privilege levels. In a properly functioning system, the login service should verify that essential system files like /etc/group exist and are accessible before proceeding with privilege management operations. However, in the affected Slackware versions, the absence of this validation check allows the login process to continue executing with elevated privileges, effectively bypassing the normal security mechanisms designed to isolate user sessions. This error handling failure creates a direct pathway for privilege escalation that operates at the system level rather than through application-level vulnerabilities, making it particularly dangerous for server environments where multiple users may attempt to log in.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass broader security implications for Linux server environments. Any local user who successfully logs into a compromised system can immediately assume root privileges, effectively neutralizing all user account security boundaries. This flaw transforms what should be a controlled access environment into a scenario where unauthorized users can gain complete system control without requiring additional exploitation techniques. The vulnerability affects systems where the /etc/group file has been removed or corrupted, which could occur through various means including system misconfiguration, malicious attacks, or accidental deletion during system maintenance operations. The consequences include complete system compromise, data theft, unauthorized access to sensitive information, and potential use as a foothold for further network infiltration activities.
The mitigation strategies for this vulnerability involve both immediate system corrections and long-term security hardening measures. System administrators should ensure that the /etc/group file remains intact and properly configured on all affected systems, typically by reinstalling the core system packages or restoring the file from a known good backup. The fundamental fix requires implementing proper error checking mechanisms within the login service to validate file existence and accessibility before proceeding with privilege operations. This approach aligns with security best practices outlined in the ATT&CK framework under privilege escalation techniques, specifically targeting the mitigation of weak file permissions and improper error handling. Additionally, implementing comprehensive system monitoring and intrusion detection measures can help identify unauthorized attempts to access systems with this vulnerability, while regular security audits should verify that critical system files remain properly configured and accessible. Organizations should also consider upgrading to newer versions of Slackware that have addressed this specific error handling flaw, as the vulnerability represents a design flaw in the authentication service that has been corrected in subsequent releases.