CVE-2018-14722 in btrfsmaintenance
Summary
by MITRE
An issue was discovered in evaluate_auto_mountpoint in btrfsmaintenance-functions in btrfsmaintenance through 0.4.1. Code execution as root can occur via a specially crafted filesystem label if btrfs-{scrub,balance,trim} are set to auto in /etc/sysconfig/btrfsmaintenance (this is not the default, though).
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Analysis
by VulDB Data Team • 03/16/2020
The vulnerability identified as CVE-2018-14722 represents a critical privilege escalation flaw within the btrfsmaintenance package ecosystem, specifically targeting the evaluate_auto_mountpoint function in btrfsmaintenance-functions. This issue affects versions through 0.4.1 and demonstrates how improper input validation can lead to arbitrary code execution with root privileges. The vulnerability exploits a design flaw in how the system handles filesystem labels during automated maintenance operations, creating a dangerous attack vector for malicious actors who can manipulate the system's behavior through carefully crafted filesystem metadata.
The technical exploitation occurs through a carefully constructed filesystem label that triggers a code execution path when btrfs maintenance operations are configured for automatic execution in the /etc/sysconfig/btrfsmaintenance configuration file. This flaw stems from insufficient sanitization of user-provided filesystem labels, allowing attackers to inject malicious commands that get executed with root privileges during the automated maintenance process. The vulnerability specifically targets the btrfs-{scrub,balance,trim} commands that are configured for automatic execution, leveraging the trust model inherent in system maintenance automation. This represents a classic command injection vulnerability where the system's assumption about label safety leads directly to privilege escalation.
The operational impact of this vulnerability is severe as it allows an attacker with access to create or modify filesystem labels to gain full root privileges on the affected system. This is particularly dangerous in environments where automated maintenance operations are enabled, as the attack can be executed without requiring additional authentication or elevated privileges beyond the ability to manipulate filesystem metadata. The vulnerability essentially undermines the security model of automated system maintenance by creating a backdoor through which malicious code can be executed with the highest system privileges. Organizations running btrfsmaintenance versions through 0.4.1 with automatic maintenance enabled are at significant risk, as the attack requires minimal prerequisites and can be executed silently in the background.
Mitigation strategies for CVE-2018-14722 should prioritize immediate patching of the btrfsmaintenance package to version 0.4.2 or later, which contains the necessary fixes for the label validation issue. System administrators should also disable automatic btrfs maintenance operations if they are not actively required, particularly by modifying the /etc/sysconfig/btrfsmaintenance configuration file to set btrfs-{scrub,balance,trim} to manual execution modes. Additional defensive measures include implementing strict filesystem label validation policies and monitoring for unusual filesystem label modifications. From a cybersecurity perspective, this vulnerability aligns with CWE-78 and CWE-20 categories, representing command injection and input validation flaws respectively, and maps to ATT&CK techniques involving privilege escalation through exploitation of system services and maintenance automation. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities in their environments.