CVE-2007-5686 in Linux
Summary
by MITRE
initscripts in rPath Linux 1 sets insecure permissions for the /var/log/btmp file, which allows local users to obtain sensitive information regarding authentication attempts. NOTE: because sshd detects the insecure permissions and does not log certain events, this also prevents sshd from logging failed authentication attempts by remote attackers.
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Analysis
by VulDB Data Team • 10/29/2017
The vulnerability described in CVE-2007-5686 represents a critical privilege escalation and information disclosure issue within the initscripts package of rPath Linux 1. This flaw stems from improper file permission settings that create a security boundary violation in the system's authentication logging infrastructure. The specific file affected is /var/log/btmp, which serves as a binary log file that records failed login attempts and other authentication events. The insecure permissions allow local users to read this sensitive information, potentially exposing details about authentication attempts that could be leveraged for further attacks.
The technical implementation of this vulnerability involves the initscripts package failing to properly set the file permissions for /var/log/btmp during system initialization. This creates an unauthorized access vector where local users can read the binary log file that normally contains sensitive authentication data. The btmp file format stores information about failed authentication attempts in a structured binary format that includes username, source IP addresses, and timestamps of login failures. When local users can access this file, they gain visibility into authentication patterns that could reveal system vulnerabilities or assist in targeted attacks.
The operational impact of this vulnerability extends beyond simple information disclosure to include a significant reduction in system security monitoring capabilities. The vulnerability creates a condition where the SSH daemon (sshd) detects the insecure permissions on the btmp file and automatically disables logging of failed authentication attempts from remote attackers. This effectively creates a blind spot in the system's security monitoring, as failed login attempts from external sources are no longer recorded in the authentication logs. This behavior aligns with the ATT&CK technique T1562.006 for "Impair Command History Logging" and demonstrates how improper file permissions can create cascading security effects that undermine core system security functions.
From a compliance and security standards perspective, this vulnerability directly relates to CWE-732: "Incorrect Permission Assignment for Critical Resource" and CWE-276: "Incorrect Permission Assignment". The flaw violates fundamental security principles of least privilege and proper access control enforcement. Organizations using rPath Linux 1 would be at risk of violating security frameworks such as NIST SP 800-53 controls that require proper file permissions and access controls. The vulnerability also impacts the CIA triad by compromising confidentiality through information disclosure and integrity through the potential for unauthorized modification of authentication logging mechanisms.
The mitigation strategy for this vulnerability requires immediate correction of file permissions for the /var/log/btmp file to ensure proper access controls are maintained. System administrators should verify that the btmp file is owned by root with restrictive permissions such as 600 or 640, preventing unauthorized access while maintaining necessary system functionality. Additionally, the initscripts package should be updated to properly implement secure default permissions during system initialization. Regular security audits should include verification of file permissions for all critical log files, particularly those that store authentication data. The remediation process should also involve monitoring for any instances where sshd might be logging failed attempts, as the original vulnerability's impact on remote authentication logging represents a significant security gap that needs to be addressed through proper permission settings and system configuration management practices.