CVE-2017-4961 in Cloud Foundry
Summary
by MITRE
An issue was discovered in Cloud Foundry Foundation BOSH Release 261.x versions prior to 261.3 and all 260.x versions. In certain cases an authenticated Director user can provide a malicious checksum that could allow them to escalate their privileges on the Director VM, aka "BOSH Director Shell Injection Vulnerabilities."
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Analysis
by VulDB Data Team • 10/16/2019
The vulnerability identified as CVE-2017-4961 represents a critical privilege escalation flaw within the Cloud Foundry Foundation BOSH release ecosystem, specifically affecting versions prior to 261.3 and all 260.x releases. This vulnerability resides in the BOSH Director component, which serves as the central management interface for Cloud Foundry deployments and orchestration. The flaw manifests when authenticated users can manipulate checksum validation processes to inject malicious commands, effectively bypassing normal access controls and elevating their privileges on the Director VM. The BOSH Director operates as a critical control plane component that manages the lifecycle of Cloud Foundry deployments, making this vulnerability particularly dangerous as it could allow attackers to gain unauthorized administrative access to the entire deployment infrastructure.
The technical exploitation of this vulnerability stems from improper input validation within the checksum verification mechanism of the BOSH Director. When users provide checksum values during deployment operations, the system fails to properly sanitize or validate these inputs before incorporating them into shell execution contexts. This creates a classic shell injection vulnerability where malicious checksum values can contain command injection payloads that get executed with elevated privileges. The vulnerability maps directly to CWE-77 and CWE-94 in the Common Weakness Enumeration catalog, specifically addressing improper input validation and code injection weaknesses. Attackers can leverage this flaw by crafting malicious checksums that, when processed by the Director, result in arbitrary command execution on the underlying VM with the privileges of the BOSH Director process, which typically runs with administrative access.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it fundamentally compromises the security posture of Cloud Foundry deployments. Once an attacker achieves elevated privileges on the Director VM, they gain complete control over all deployments managed by that Director instance, including the ability to modify deployment manifests, access sensitive configuration data, and potentially compromise the entire Cloud Foundry foundation. This vulnerability directly aligns with ATT&CK technique T1059.001 for command and scripting interpreter execution, as well as T1068 for exploit for privilege escalation. The implications are severe for organizations relying on Cloud Foundry for application deployment, as the compromise of a single Director instance can lead to widespread access to multiple applications and services hosted within the platform, potentially affecting thousands of end users and applications.
Organizations should immediately implement mitigations including upgrading to BOSH release versions 261.3 or later, which contain patches addressing the checksum validation vulnerability. Network segmentation should be implemented to restrict access to BOSH Director endpoints, limiting exposure to authenticated users only. Additional security controls such as multi-factor authentication for Director access and regular audit logging of Director operations should be enforced. The vulnerability highlights the importance of proper input validation in security-critical components and demonstrates how seemingly minor validation flaws can result in major privilege escalation capabilities. Regular security assessments of deployment management systems and adherence to secure coding practices are essential for preventing similar vulnerabilities in cloud infrastructure components. Organizations should also consider implementing automated vulnerability scanning tools that can detect and alert on potentially malicious checksum values or command injection attempts within their Cloud Foundry environments.