CVE-2025-9276: Cockroach-k8s-request-cert Auth Bypass

CVE-2025-9276 Overview

CVE-2025-9276 is a critical authentication bypass vulnerability affecting the Cockroach Labs cockroach-k8s-request-cert container image. This vulnerability allows remote attackers to bypass authentication on systems running the affected container due to a misconfiguration in the system shadow file where the root user has a blank password set.

The flaw stems from an insecure default configuration that leaves the root account without password protection. An attacker with network access to the affected container can leverage this vulnerability to gain unauthorized root-level access, potentially compromising the entire Kubernetes cluster and any CockroachDB deployments it manages.

Critical Impact

Remote attackers can bypass authentication and gain root access to affected container images without any credentials, enabling complete system compromise.

Affected Products

• Cockroach Labs cockroach-k8s-request-cert container image

Discovery Timeline

• 2025-09-02 - CVE-2025-9276 published to NVD
• 2026-01-30 - Last updated in NVD database

Technical Details for CVE-2025-9276

Vulnerability Analysis

This authentication bypass vulnerability exists due to a fundamental security misconfiguration in the container image's /etc/shadow file. The root user account is configured with an empty password field, effectively allowing anyone with network access to authenticate as root without providing credentials.

The vulnerability is particularly severe in Kubernetes environments where the cockroach-k8s-request-cert container is used to manage certificate requests for CockroachDB clusters. Successful exploitation grants attackers the highest level of system privileges within the container, potentially enabling lateral movement to other pods, access to Kubernetes secrets, and compromise of the underlying CockroachDB infrastructure.

This vulnerability was tracked by the Zero Day Initiative as ZDI-CAN-22195 before public disclosure as ZDI-25-855.

Root Cause

The root cause is an insecure default configuration (CWE-258: Empty Password in Configuration File) in the container image build process. During container image creation, the /etc/shadow file was configured with an empty password hash for the root user, leaving the account effectively unprotected. This type of misconfiguration is especially dangerous in containerized environments where network exposure may be unintentionally broader than expected.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability through any service that accepts authentication against the system's shadow file, such as SSH if enabled, or through container exec mechanisms if the attacker has access to the Kubernetes API. The attack complexity is low since the attacker simply needs to attempt authentication as root with an empty or null password.

The exploitation flow involves:

1. Identifying a running instance of the vulnerable cockroach-k8s-request-cert container
2. Connecting to any authentication service exposed by the container
3. Attempting to authenticate as root with no password
4. Gaining full root access to the container environment

Detection Methods for CVE-2025-9276

Indicators of Compromise

• Unexpected authentication events for the root user without corresponding password authentication
• Container exec sessions initiated from unauthorized sources targeting cockroach-k8s-request-cert pods
• Unusual process execution or file modifications within the affected container
• Kubernetes audit logs showing unauthorized access to CockroachDB-related secrets or certificates

Detection Strategies

• Monitor Kubernetes audit logs for suspicious exec commands targeting cockroach-k8s-request-cert containers
• Implement container image scanning to detect empty password configurations in /etc/shadow
• Deploy runtime security monitoring to detect root login events within containers
• Configure alerts for any successful root authentication without proper credential verification

Monitoring Recommendations

• Enable verbose logging for all authentication attempts within Kubernetes pods
• Implement SentinelOne Singularity Cloud Workload Security for real-time container runtime protection
• Configure network policies to restrict unexpected inbound connections to affected containers
• Deploy admission controllers to prevent deployment of container images with known vulnerabilities

How to Mitigate CVE-2025-9276

Immediate Actions Required

• Identify all deployments using the vulnerable cockroach-k8s-request-cert container image
• Implement network policies to restrict access to affected containers until patching is complete
• Review Kubernetes audit logs for signs of exploitation
• Consider temporarily replacing the vulnerable container with a custom-built secure alternative

Patch Information

Consult the Zero Day Initiative Advisory ZDI-25-855 for the latest patch information and updated container image versions from Cockroach Labs. Organizations should update to a patched version of the cockroach-k8s-request-cert container image as soon as one becomes available.

Workarounds

• Build a custom container image with a properly secured root password or disabled root login
• Implement Kubernetes NetworkPolicies to restrict network access to affected pods
• Use Pod Security Policies or Pod Security Standards to prevent privileged container execution
• Deploy a service mesh with mutual TLS to add an additional authentication layer

# Configuration example - Kubernetes NetworkPolicy to restrict pod access
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: restrict-cockroach-cert-pod
  namespace: cockroachdb
spec:
  podSelector:
    matchLabels:
      app: cockroach-k8s-request-cert
  policyTypes:
  - Ingress
  ingress:
  - from:
    - podSelector:
        matchLabels:
          app: cockroachdb