Introduction
Remote attackers can gain root access to Kubernetes certificate management containers without any authentication if organizations are running the vulnerable Cockroach Labs cockroach-k8s-request-cert image. This critical flaw allows adversaries to bypass all authentication barriers, posing a severe risk to any infrastructure using this container for CockroachDB deployments.
About Cockroach Labs: Cockroach Labs is a prominent provider of distributed SQL database technology, best known for CockroachDB. Their solutions are widely adopted in cloud-native and Kubernetes environments, powering mission-critical workloads for organizations ranging from startups to large enterprises. The company is recognized for its focus on resilience and scalability in the database space.
Technical Information
The vulnerability (CVE-2025-9276) is rooted in the configuration of the /etc/shadow file within the cockroach-k8s-request-cert container image. Specifically, the root user entry in this file contains an empty password field. This misconfiguration means any authentication attempt as root will succeed, regardless of the password provided (or lack thereof).
- Vulnerable mechanism:
- The
/etc/shadowfile governs password authentication for system users. A blank password for root disables password checks entirely. - Attackers can authenticate as root via any interface that relies on system authentication, such as SSH, local console, or services using PAM.
- The vulnerability is classified under CWE-258 (Empty Password in Configuration File).
- The
No code snippet is available in public sources for this vulnerability.
Proof of Concept
The vulnerability in the Cockroach Labs cockroach-k8s-request-cert container image arises from an improperly configured system shadow file, where the root user is assigned a blank password. This misconfiguration allows remote attackers to bypass authentication mechanisms, granting unauthorized access to the system.
In practical terms, an attacker can exploit this vulnerability by attempting to log in as the root user without providing a password. Due to the empty password field, the system permits access, effectively nullifying any authentication barriers.
This issue underscores the critical importance of secure default configurations, especially concerning authentication credentials. Administrators should ensure that all user accounts, particularly those with elevated privileges like root, are assigned strong, non-empty passwords to prevent unauthorized access.
Reference: ZDI-25-855
Detection Methods
Detecting unauthorized access due to an empty root password in the Cockroach Labs cockroach-k8s-request-cert container image involves several strategies:
1. Monitoring Authentication Logs:
Regularly review system authentication logs to identify any instances of root logins without password authentication. Unusual or unexpected root access entries can indicate exploitation of the vulnerability.
2. Implementing File Integrity Monitoring (FIM):
Deploy FIM tools to monitor changes to critical system files, including the /etc/shadow file. Alerts should be configured for any unauthorized modifications, such as the presence of blank password fields for the root user.
3. Utilizing Security Information and Event Management (SIEM) Systems:
Configure SIEM systems to detect patterns associated with unauthorized root access. This includes setting up alerts for:
- Multiple root login attempts without password prompts.
- Access to sensitive files or directories by the root user without prior authorization.
4. Conducting Regular Vulnerability Scans:
Perform routine scans of container images and deployed systems to identify configurations with empty root passwords. Automated scanning tools can help detect and remediate such vulnerabilities promptly.
5. Reviewing Container Configurations:
Examine the configuration of deployed containers to ensure that default credentials are not in use. Specifically, verify that the cockroach-k8s-request-cert container does not have an empty root password set.
6. Implementing Access Controls:
Restrict access to the cockroach-k8s-request-cert container and associated systems. Ensure that only authorized personnel have the necessary permissions to modify configurations or access sensitive components.
By proactively monitoring and auditing system configurations and access logs, organizations can detect and mitigate potential exploitation of this authentication bypass vulnerability.
Reference: ZDI-25-855
Affected Systems and Versions
- Product: Cockroach Labs cockroach-k8s-request-cert container image
- All versions of the cockroach-k8s-request-cert container image are affected
- The image is no longer supported by Cockroach Labs
- Any deployment using this image for certificate management in Kubernetes is vulnerable
Vendor Security History
Cockroach Labs has a documented vulnerability management process and has addressed previous security issues in core CockroachDB products. However, in this case, the vendor did not respond to initial disclosure attempts and instead stated that the affected container image is no longer supported, leaving remediation to users.