CVE-2018-15664 in Azure Kubernetes Service
Summary
by MITRE
In Docker through 18.06.1-ce-rc2, the API endpoints behind the 'docker cp' command are vulnerable to a symlink-exchange attack with Directory Traversal, giving attackers arbitrary read-write access to the host filesystem with root privileges, because daemon/archive.go does not do archive operations on a frozen filesystem (or from within a chroot).
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Analysis
by VulDB Data Team • 08/09/2024
The vulnerability identified as CVE-2018-15664 represents a critical security flaw in Docker versions up to 18.06.1-ce-rc2 that directly impacts the container daemon's handling of file operations. This weakness stems from improper validation within the daemon/archive.go component which fails to properly secure archive operations when dealing with symbolic links and directory traversal scenarios. The flaw allows attackers to exploit the docker cp command functionality to gain unauthorized access to the host filesystem with root privileges, creating a severe privilege escalation vector that bypasses normal container isolation mechanisms.
The technical implementation of this vulnerability exploits the fundamental design flaw in how Docker handles symbolic link resolution during archive operations. When the daemon processes file copying operations through the docker cp command, it does not adequately verify or sanitize symbolic links that may point to arbitrary locations on the host filesystem. This allows an attacker to create a malicious symlink structure that, when traversed during the copy operation, redirects the operation to unintended host directories. The vulnerability specifically occurs because the archive operations are not performed on a frozen filesystem or within a chroot environment, leaving the underlying host filesystem exposed to manipulation through crafted symbolic links.
The operational impact of this vulnerability is devastating for containerized environments as it completely undermines the security model that containers are designed to provide. An attacker with access to execute docker cp commands can leverage this flaw to read sensitive files from the host system, modify critical system components, and potentially establish persistent access. The vulnerability enables arbitrary read-write access to the entire host filesystem with root privileges, effectively nullifying container isolation and allowing attackers to compromise the host machine. This creates a pathway for further attacks including privilege escalation, lateral movement, and data exfiltration from the compromised host environment.
From a cybersecurity framework perspective, this vulnerability maps directly to CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-36 (Absolute Path Traversal) while aligning with ATT&CK technique T1059.001 (Command and Scripting Interpreter: PowerShell) and T1078 (Valid Accounts) as attackers can leverage this to escalate privileges and maintain access. Organizations running affected Docker versions face significant risk of complete system compromise, particularly in multi-tenant environments or when containers are run with elevated privileges. The vulnerability demonstrates the critical importance of proper input validation and containment of file operations within containerized environments, as the flaw exists at the core daemon functionality that handles file system interactions.
Mitigation strategies for this vulnerability require immediate patching of Docker daemon versions to address the underlying archive handling logic. Organizations should implement strict access controls limiting who can execute docker cp commands and consider running containers with reduced privileges. Network segmentation and monitoring should be enhanced to detect unusual file system access patterns that might indicate exploitation attempts. Additionally, container orchestration platforms should be configured to disable or restrict the docker cp functionality when possible, and regular security audits should verify that no symbolic link manipulation occurs during container operations. The fix implemented in later Docker versions involves proper handling of symbolic links through filesystem freezing or chroot operations to prevent traversal attacks during archive processing.