CVE-2016-1581 in lxd
Summary
by MITRE
LXD before 2.0.2 uses world-readable permissions for /var/lib/lxd/zfs.img when setting up a loop based ZFS pool, which allows local users to copy and read data from arbitrary containers via unspecified vectors.
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Analysis
by VulDB Data Team • 08/23/2022
The vulnerability identified as CVE-2016-1581 affects LXD versions prior to 2.0.2 and represents a critical privilege escalation and data exposure issue within containerized environments. This flaw stems from improper file permission handling during the setup of loop-based ZFS pools, creating a significant security gap that adversaries can exploit to gain unauthorized access to containerized data. The issue specifically involves the /var/lib/lxd/zfs.img file which is created with world-readable permissions, fundamentally undermining the security model of container isolation.
The technical implementation of this vulnerability occurs during the initialization process of LXD's ZFS storage backend where the system creates a loop device backed by a ZFS image file. When the permissions are incorrectly set to world-readable, any local user on the system can access this file directly through the filesystem. This misconfiguration enables attackers to copy the ZFS image and subsequently mount it to access the underlying container filesystems. The unspecified vectors mentioned in the description indicate that multiple attack paths exist, potentially including direct file system manipulation, mounting techniques, or exploitation of the loop device mechanism itself. This represents a classic case of insecure default permissions that violates fundamental security principles of least privilege and proper access control enforcement.
The operational impact of CVE-2016-1581 extends beyond simple data theft to encompass complete container compromise and potential lateral movement within affected systems. Local users who exploit this vulnerability can effectively bypass container isolation mechanisms, gaining access to sensitive data stored within other containers running on the same host. This creates a significant risk for multi-tenant environments where containerized applications from different users or organizations share the same infrastructure. The vulnerability directly impacts the security posture of cloud deployments, container orchestration platforms, and any system relying on LXD for container management. From an attack perspective, this vulnerability aligns with ATT&CK techniques related to privilege escalation and credential access, specifically targeting the use of insecure file permissions to gain unauthorized access to protected resources.
This vulnerability maps directly to CWE-732: Incorrect Permission Assignment for Critical Resource, which classifies the flaw as a fundamental misconfiguration that allows unauthorized access to protected system resources. The issue demonstrates poor security hygiene in the storage initialization process and highlights the importance of proper permission management in containerized environments. Organizations running affected LXD versions face a heightened risk of data breaches, compliance violations, and potential system compromise. The impact is particularly severe in cloud environments where multiple users share the same physical infrastructure, as this vulnerability could enable a single compromised local account to access data from numerous containers across the system. The remediation strategy involves upgrading to LXD 2.0.2 or later versions where the permission handling has been corrected to prevent world-readable access to the ZFS image file. Additionally, system administrators should conduct immediate audits of existing installations to identify and correct any lingering instances of the vulnerable file permissions, ensuring that all container storage images maintain appropriate access controls.