CVE-2017-5985 in Linux Containers
Summary
by MITRE
lxc-user-nic in Linux Containers (LXC) allows local users with a lxc-usernet allocation to create network interfaces on the host and choose the name of those interfaces by leveraging lack of netns ownership check.
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Analysis
by VulDB Data Team • 09/07/2020
The vulnerability identified as CVE-2017-5985 resides within the Linux Containers (LXC) framework, specifically affecting the lxc-user-nic utility that manages network interface allocation for containerized environments. This issue represents a significant privilege escalation concern that undermines the fundamental security boundaries between host and container systems. The flaw manifests when local users who have been granted lxc-usernet allocation permissions can exploit a missing netns ownership validation mechanism to create network interfaces on the host system with arbitrary names. This capability directly violates the principle of least privilege and container isolation that LXC aims to enforce.
The technical root cause of this vulnerability stems from insufficient validation within the lxc-user-nic utility's network namespace handling procedures. When users with limited container network permissions attempt to create network interfaces, the system fails to verify that the requesting user actually owns the target network namespace. This missing ownership check creates a pathway for malicious users to manipulate the network interface naming process and potentially interfere with host network operations. The vulnerability operates at the kernel level where network namespace management occurs, making it particularly dangerous as it can be exploited to disrupt network services or establish unauthorized communication channels between containers and the host system.
The operational impact of CVE-2017-5985 extends beyond simple privilege escalation to encompass potential network disruption and data exfiltration capabilities. An attacker who successfully exploits this vulnerability could create network interfaces with names that conflict with existing host interfaces, leading to routing confusion and potential network outages. Additionally, the ability to create arbitrary network interface names allows for more sophisticated attacks such as man-in-the-middle scenarios where the attacker can intercept traffic between containers and the host. This vulnerability aligns with CWE-264, which addresses permissions, privileges, and access control issues, and represents a clear violation of the principle of least privilege in containerized environments. The threat landscape for this vulnerability is particularly concerning as it can be exploited by users who already have some level of access to container resources, making it a valuable stepping stone for more comprehensive attacks.
Mitigation strategies for CVE-2017-5985 should focus on both immediate patching and operational hardening measures. The primary solution involves updating to LXC versions that include proper netns ownership validation checks within the lxc-user-nic utility. Organizations should also implement strict network namespace management policies that limit the scope of user permissions and regularly audit container network configurations. Network monitoring should be enhanced to detect anomalous interface creation patterns, and access controls should be reviewed to ensure that only authorized users can obtain lxc-usernet allocation permissions. This vulnerability demonstrates the importance of maintaining robust security boundaries in containerized environments and aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', making it a critical target for defensive security measures.