CVE-2015-3243 in rsyslog
Summary
by MITRE
rsyslog uses weak permissions for generating log files, which allows local users to obtain sensitive information by reading files in /var/log/cron.
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Analysis
by VulDB Data Team • 01/06/2021
The vulnerability identified as CVE-2015-3243 affects the rsyslog logging daemon implementation on unix-like systems where the software fails to properly enforce file permissions during log file creation. This flaw stems from the rsyslog service's default configuration that generates log files with overly permissive access controls, specifically allowing world-readable permissions that should be restricted to prevent unauthorized information disclosure. The issue manifests when rsyslog creates log files in the /var/log/cron directory, which typically contains sensitive system logging information including cron job executions, user activities, and potentially authentication events that could reveal system access patterns or user behavior.
The technical root cause of this vulnerability aligns with CWE-732, which describes improper permission assignment for critical resources, and represents a classic case of insufficient access control mechanisms within the logging infrastructure. When rsyslog creates log files without properly setting restrictive file permissions, it inadvertently exposes sensitive information to any local user who can access the filesystem. The weak permissions typically result in log files being created with read permissions for all users, allowing any local attacker to read potentially sensitive information contained within these logs. This includes but is not limited to system commands executed through cron jobs, user login activities, and other operational details that could be leveraged for further exploitation or system compromise.
From an operational perspective, this vulnerability creates a significant information disclosure risk that can be exploited by local attackers to gain insights into system operations, user activities, and potential security weaknesses. The impact extends beyond simple information disclosure as the exposed log data could reveal patterns of system usage, user behaviors, and potentially sensitive operational details that could be used in conjunction with other attacks. Attackers could use this information to identify active users, determine system scheduling patterns, or uncover other system configurations that might be exploitable through additional attack vectors. The vulnerability particularly affects systems where rsyslog is configured to log cron activities, making the /var/log/cron directory a prime target for information gathering.
The mitigation strategies for CVE-2015-3243 should focus on implementing proper file permission controls within the rsyslog configuration, ensuring that log files are created with restrictive permissions that limit access to authorized users and processes only. System administrators should configure rsyslog to enforce proper umask settings and file permission controls during log file creation, typically requiring permissions of 600 or 640 for log files rather than the default 644 or more permissive settings. Additionally, implementing proper log rotation policies with appropriate ownership and permission settings helps maintain security over time. Organizations should also consider implementing monitoring for unauthorized access attempts to sensitive log directories and establish regular security audits to verify that logging configurations maintain appropriate access controls. This vulnerability demonstrates the importance of following security best practices for system logging components and highlights the need for proper file permission management as outlined in various security frameworks including the CIS Linux Benchmark and NIST guidelines for secure system configuration.