CVE-2019-11253 : Security Advisory and Response

Kubernetes API Server JSON/YAML parsing vulnerable to resource exhaustion attack.

Understanding CVE-2019-11253

The Kubernetes API server in versions v1.0-1.12 and versions before v1.13.12, v1.14.8, v1.15.5, and v1.16.2 has a flaw in its input validation, allowing authorized users to send malicious payloads in YAML or JSON format.

What is CVE-2019-11253?

The vulnerability in Kubernetes API server allows for resource exhaustion attacks due to improper input validation, potentially crashing the server.

The Impact of CVE-2019-11253

Authorized users can exploit the flaw to cause excessive CPU or memory usage, leading to server unavailability.
Default RBAC policy in earlier versions permits anonymous users to trigger the vulnerability.

Technical Details of CVE-2019-11253

Vulnerability Description

Improper input validation in Kubernetes API server versions v1.0-1.12 and prior to v1.13.12, v1.14.8, v1.15.5, and v1.16.2.

Affected Systems and Versions

Kubernetes versions prior to 1.13.12, 1.14.8, 1.15.5, and 1.16.2.

Exploitation Mechanism

Authorized users can send malicious YAML or JSON payloads, causing CPU or memory overload.

Mitigation and Prevention

Immediate Steps to Take

Mitigate exposure by removing write permissions from unauthenticated users.

Long-Term Security Practices

Regularly update Kubernetes to patched versions.
Implement strict RBAC policies to limit unauthorized access.
Monitor API server performance for unusual resource consumption.

Patching and Updates

Apply patches provided by Kubernetes to address the input validation vulnerability.