CVE-2015-3630 in Docker
Summary
by MITRE
Docker Engine before 1.6.1 uses weak permissions for (1) /proc/asound, (2) /proc/timer_stats, (3) /proc/latency_stats, and (4) /proc/fs, which allows local users to modify the host, obtain sensitive information, and perform protocol downgrade attacks via a crafted image.
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Analysis
by VulDB Data Team • 05/17/2022
The vulnerability identified as CVE-2015-3630 represents a critical privilege escalation issue within Docker Engine versions prior to 1.6.1, where the container runtime fails to properly enforce access controls on specific host kernel interfaces. This weakness stems from the improper permission settings applied to four distinct proc filesystem entries including /proc/asound for audio subsystem information, /proc/timer_stats for timer statistics, /proc/latency_stats for latency measurements, and /proc/fs for filesystem-related data. These paths expose sensitive kernel information and control mechanisms that should remain restricted to privileged processes.
The technical flaw exploited by this vulnerability lies in the insufficient access control mechanisms implemented by Docker's container runtime environment. When containers are launched without proper privilege isolation, these proc filesystem entries inherit weak permissions that allow unprivileged container processes to read sensitive kernel information or potentially modify system behavior. The vulnerability specifically affects the Linux kernel's proc filesystem implementation where these particular paths should normally be restricted to root access or specific privileged processes. Attackers can leverage this weakness by crafting malicious container images that attempt to access these restricted interfaces, potentially enabling information disclosure, privilege escalation, or protocol downgrade attacks that compromise the host system's integrity.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides local attackers with pathways to modify host system behavior and potentially escalate privileges. When exploited, attackers can access audio subsystem information that may reveal system configuration details, access timer statistics that could aid in timing attacks, or manipulate filesystem-related data that might affect system stability. The protocol downgrade capabilities mentioned in the vulnerability description suggest that attackers could potentially manipulate kernel-level protocols or communication channels that are normally protected from unauthorized access. This vulnerability particularly affects containerized environments where multiple users or applications share the same host system, creating opportunities for privilege escalation attacks that could compromise the entire host infrastructure.
Organizations should immediately update their Docker Engine installations to version 1.6.1 or later to address this vulnerability, as the patch implements proper permission controls on the affected proc filesystem entries. System administrators should also review existing container deployments to ensure that no containers are running with unnecessary privileges that could expose these weaknesses. The vulnerability aligns with CWE-276, which addresses improper permissions for critical resources, and maps to ATT&CK technique T1068, which covers local privilege escalation through kernel exploits. Additional mitigations include implementing proper container runtime security policies, restricting container capabilities, and monitoring for unauthorized access attempts to kernel interfaces. Organizations should also consider implementing container runtime security solutions that can detect and prevent exploitation attempts targeting these specific proc filesystem vulnerabilities, as well as conducting regular security assessments of their containerized environments to identify potential privilege escalation pathways.