CVE-2018-20699 in Docker
Summary
by MITRE
Docker Engine before 18.09 allows attackers to cause a denial of service (dockerd memory consumption) via a large integer in a --cpuset-mems or --cpuset-cpus value, related to daemon/daemon_unix.go, pkg/parsers/parsers.go, and pkg/sysinfo/sysinfo.go.
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Analysis
by VulDB Data Team • 06/26/2023
This vulnerability exists in Docker Engine versions prior to 18.09 and represents a denial of service condition that can be triggered by manipulating cpuset parameters. The flaw specifically affects the daemon process handling of --cpuset-mems and --cpuset-cpus command line options, where large integer values can cause excessive memory consumption in the dockerd process. The vulnerability stems from inadequate input validation and parsing of cpuset values within the Docker daemon's core components, particularly in the daemon_unix.go file which manages unix-specific daemon operations. The issue is exacerbated by the way the system processes these parameters during container creation and resource allocation phases.
The technical implementation of this vulnerability involves the parsing logic in pkg/parsers/parsers.go and the system information handling in pkg/sysinfo/sysinfo.go where malformed or excessively large integer values in cpuset specifications are not properly validated or capped. When an attacker provides a large integer value for cpuset-mems or cpuset-cpus parameters, the Docker daemon attempts to process this value through its internal parsing mechanisms without sufficient bounds checking. This leads to memory allocation patterns that can consume excessive resources, potentially causing the dockerd process to crash or become unresponsive. The vulnerability is classified under CWE-129 as an insufficient input validation, specifically dealing with improper validation of input ranges and sizes.
The operational impact of this vulnerability extends beyond simple denial of service as it can affect the entire Docker host system. When exploited, the excessive memory consumption can cause the dockerd daemon to exhaust available system memory, leading to system instability and potential service disruption. This affects container orchestration environments where multiple containers might be launched with malicious cpuset values, or where an attacker has access to container creation capabilities. The vulnerability is particularly concerning in multi-tenant environments or shared hosting scenarios where one compromised container could potentially affect the entire Docker host. The issue falls under the ATT&CK technique T1499.001 for network denial of service and can be leveraged as part of broader attack chains targeting containerized environments.
Mitigation strategies for this vulnerability require immediate patching of Docker Engine to version 18.09 or later where proper input validation has been implemented. System administrators should also implement monitoring for unusual memory consumption patterns in dockerd processes and establish strict input validation policies for cpuset parameters in container orchestration frameworks. Additionally, implementing resource limits and quotas for container creation can prevent malicious exploitation by restricting the ability to specify excessively large cpuset values. Organizations should also consider implementing container runtime security policies that validate all resource allocation parameters before container instantiation, and regularly audit their Docker host configurations to ensure proper security controls are in place. The vulnerability demonstrates the importance of robust input validation in system-level components and highlights the need for comprehensive security testing of container orchestration platforms.