CVE-2015-1335 in lxc
Summary
by MITRE
lxc-start in lxc before 1.0.8 and 1.1.x before 1.1.4 allows local container administrators to escape AppArmor confinement via a symlink attack on a (1) mount target or (2) bind mount source.
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Analysis
by VulDB Data Team • 06/20/2022
The vulnerability identified as CVE-2015-1335 affects the Linux Containers (lxc) project, specifically the lxc-start utility, which is critical for container initialization and management. This issue exists in versions prior to 1.0.8 and 1.1.x before 1.1.4, representing a significant security flaw that undermines the confinement mechanisms designed to isolate containerized processes. The vulnerability stems from improper handling of symbolic links during mount operations, creating a pathway for privilege escalation and bypass of security controls that are fundamental to container security models.
The technical flaw manifests through two distinct attack vectors involving AppArmor confinement bypass. Attackers with local administrative privileges within a container can exploit this vulnerability by creating malicious symbolic links that point to sensitive system resources. When lxc-start processes mount operations, it follows these symbolic links without proper validation, allowing the container administrator to manipulate mount targets or bind mount sources in ways that were not intended. This symlink attack enables the escape from the container's confined environment, potentially granting access to host system resources, files, and processes that should remain isolated from containerized applications.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the security model of containerization systems that rely on AppArmor for process confinement. Container administrators who believe their systems are protected by AppArmor policies may be unaware that local attackers can bypass these protections through simple file system manipulation. This vulnerability is particularly dangerous in multi-tenant environments where different users share the same host system, as it allows one container's administrator to potentially access or compromise other containers or the host system itself. The attack requires only local access within a container, making it accessible to any user who can execute commands inside a container, regardless of their initial privileges.
The vulnerability aligns with CWE-59 and CWE-22 categories, specifically addressing weaknesses in file system path resolution and symbolic link handling within container management systems. From an ATT&CK framework perspective, this represents a privilege escalation technique under T1068 (Local Privilege Escalation) and potentially T1565 (Data Manipulation) when attackers manipulate mount points to gain unauthorized access to system resources. Organizations using lxc containers should immediately upgrade to versions 1.0.8 or 1.1.4 and later to address this issue. Additional mitigations include implementing strict file system permissions, monitoring for suspicious symbolic link creation, and considering alternative containerization technologies that have addressed similar issues. The vulnerability demonstrates the critical importance of proper input validation and path resolution in container management systems, as inadequate protection mechanisms can lead to complete compromise of container isolation properties.