CVE-2015-5186 in Audit
Summary
by MITRE
Audit before 2.4.4 in Linux does not sanitize escape characters in filenames.
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Analysis
by VulDB Data Team • 01/11/2021
The vulnerability identified as CVE-2015-5186 affects the Linux audit subsystem version 2.4.4 and earlier, specifically targeting how the audit framework handles filename sanitization during logging operations. This issue resides within the auditd daemon's processing of audit records, where escape characters present in filenames are not properly sanitized before being written to audit logs. The flaw represents a significant security concern as it allows for potential log injection attacks that could compromise the integrity and confidentiality of audit data. When audit records contain unescaped special characters, particularly those used in shell contexts, malicious actors can exploit this weakness to manipulate audit log contents or inject arbitrary commands that may be executed by log processing tools.
The technical implementation of this vulnerability stems from inadequate input validation within the audit subsystem's filename handling logic. When filenames containing escape sequences such as backslashes, quotes, or other special shell characters are processed by the audit framework, these characters are not properly escaped or removed from the audit log output. This behavior creates a path for attackers who can craft filenames containing malicious escape sequences that, when processed by audit log viewers or parsing tools, could result in unintended command execution or log manipulation. The vulnerability operates at the application layer within the Linux kernel's audit subsystem and affects all systems running affected versions of the audit framework.
The operational impact of CVE-2015-5186 extends beyond simple log corruption, potentially enabling attackers to bypass audit controls and hide malicious activities within audit logs. Attackers could craft filenames that, when logged, would allow them to inject commands into log processing pipelines or manipulate log analysis tools to display false information. This vulnerability directly impacts the integrity of audit trails, which are critical for security monitoring and compliance requirements. The flaw also creates potential for privilege escalation scenarios where attackers manipulate audit logs to cover their tracks or confuse security analysts during incident response activities. Organizations relying on audit logs for security monitoring, forensic analysis, and compliance verification face significant risks from this vulnerability, as it undermines the trustworthiness of audit data that security teams depend upon for detecting and responding to security incidents.
Mitigation strategies for CVE-2015-5186 should prioritize immediate patching of affected systems to version 2.4.4 or later of the Linux audit framework, which includes proper sanitization of escape characters in filenames. System administrators should implement additional monitoring of audit log integrity and consider deploying log integrity checking tools to detect potential tampering. Network segmentation and access controls should be strengthened to limit who can modify audit configurations or create files that might be processed by the audit subsystem. Organizations should also review their log processing pipelines to ensure that audit log parsers and viewers are not vulnerable to command injection through malformed input. The vulnerability aligns with CWE-117, which addresses improper output neutralization for logs, and maps to ATT&CK technique T1070.002, which covers the manipulation of audit logs to evade detection. Regular security assessments of audit configurations and continuous monitoring of audit log integrity should be implemented as part of comprehensive security operations to prevent exploitation of similar vulnerabilities in the future.