CVE-2021-36782: SUSE Rancher Information Disclosure Flaw

CVE-2021-36782 Overview

A Cleartext Storage of Sensitive Information vulnerability exists in SUSE Rancher that allows authenticated users with various roles—including Cluster Owners, Cluster Members, Project Owners, Project Members, and User Base—to retrieve plaintext versions of sensitive data through the Kubernetes API. This vulnerability represents a significant security flaw in how Rancher manages and stores sensitive credential information within Kubernetes clusters.

Critical Impact

Authenticated users can access sensitive data in plaintext through the Kubernetes API, potentially exposing credentials, secrets, and other confidential information stored within Rancher-managed clusters.

Affected Products

• SUSE Rancher versions prior to 2.5.16
• SUSE Rancher versions prior to 2.6.7

Discovery Timeline

• 2022-09-07 - CVE CVE-2021-36782 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-36782

Vulnerability Analysis

This vulnerability falls under CWE-312 (Cleartext Storage of Sensitive Information), a critical security weakness where applications store sensitive data without proper encryption or protection mechanisms. In the context of SUSE Rancher, the vulnerability allows authenticated users across multiple privilege levels to leverage the Kubernetes API to retrieve sensitive information that should be encrypted or otherwise protected.

The impact of this vulnerability is severe because it affects users with relatively low privilege requirements. Even standard authenticated users with basic roles such as Project Members or User Base can exploit this flaw to access sensitive data that should be restricted to higher-privileged administrators. This creates a significant information disclosure risk in multi-tenant Kubernetes environments managed by Rancher.

Root Cause

The root cause stems from improper handling of sensitive information storage within Rancher's Kubernetes integration layer. Sensitive data such as credentials, API tokens, and configuration secrets are stored in a manner that allows retrieval in plaintext through standard Kubernetes API calls. This violates the security principle that sensitive information should be encrypted at rest and only accessible to authorized processes with legitimate need-to-know requirements.

Attack Vector

The attack vector is network-based and requires only low-privilege authenticated access to the Rancher-managed Kubernetes cluster. An attacker with any authenticated role (Cluster Owner, Cluster Member, Project Owner, Project Member, or User Base) can craft API requests to the Kubernetes API to enumerate and retrieve sensitive data stored in cleartext.

The attack can be executed remotely without user interaction, and the scope extends beyond the vulnerable component, potentially affecting other resources and systems that rely on the exposed credentials. This is particularly dangerous in shared Kubernetes environments where users from different teams or organizations may have access to the same Rancher instance.

Detection Methods for CVE-2021-36782

Indicators of Compromise

• Unusual Kubernetes API requests targeting secrets, configmaps, or custom resources that store sensitive data
• Elevated API query activity from user accounts with lower privilege roles
• Access patterns showing bulk retrieval of sensitive resources across multiple namespaces
• Audit log entries showing secret or credential access by unexpected user principals

Detection Strategies

• Enable and monitor Kubernetes API audit logging for all secret and sensitive resource access
• Implement anomaly detection for API access patterns that deviate from established baselines
• Configure alerts for any access to sensitive resources by non-administrative roles
• Deploy SentinelOne Singularity Cloud to provide runtime visibility into Kubernetes cluster activity

Monitoring Recommendations

• Continuously monitor Rancher server logs and Kubernetes audit logs for suspicious API calls
• Implement real-time alerting for credential access events outside of normal application workflows
• Establish baseline user behavior profiles to detect anomalous data retrieval activities
• Review and audit access logs regularly for evidence of sensitive data enumeration attempts

How to Mitigate CVE-2021-36782

Immediate Actions Required

• Upgrade SUSE Rancher to version 2.5.16 or later for the 2.5.x release train
• Upgrade SUSE Rancher to version 2.6.7 or later for the 2.6.x release train
• Rotate all credentials and secrets that may have been exposed through this vulnerability
• Review Kubernetes audit logs to identify any potential unauthorized access to sensitive data

Patch Information

SUSE has released security patches addressing this vulnerability. Affected organizations should upgrade to Rancher version 2.5.16 or later for the 2.5.x branch, or version 2.6.7 or later for the 2.6.x branch. Detailed patch information and upgrade instructions are available through the SUSE Bug Report #1193988 and the GitHub Security Advisory GHSA-g7j7-h4q8-8w2f.

Workarounds

• Implement strict Role-Based Access Control (RBAC) policies to limit which users can query Kubernetes secrets and sensitive resources
• Apply network segmentation to restrict API access to trusted networks only
• Use Kubernetes Network Policies to limit pod-to-pod and external communication
• Consider implementing additional encryption layers for secrets management using external solutions such as HashiCorp Vault or sealed-secrets

# Review current Rancher version
kubectl get deployment rancher -n cattle-system -o jsonpath='{.spec.template.spec.containers[0].image}'

# Audit secret access in Kubernetes
kubectl get secrets --all-namespaces -o wide

# Enable Kubernetes API audit logging (add to kube-apiserver configuration)
# --audit-log-path=/var/log/kubernetes/audit.log
# --audit-policy-file=/etc/kubernetes/audit-policy.yaml