CVE-2018-1098 in etcd
Summary
by MITRE
A cross-site request forgery flaw was found in etcd 3.3.1 and earlier. An attacker can set up a website that tries to send a POST request to the etcd server and modify a key. Adding a key is done with PUT so it is theoretically safe (can't PUT from an HTML form or such) but POST allows creating in-order keys that an attacker can send.
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Analysis
by VulDB Data Team • 01/21/2020
The vulnerability described in CVE-2018-1098 represents a critical cross-site request forgery flaw affecting etcd versions 3.3.1 and earlier. This issue arises from the improper handling of HTTP POST requests within the etcd key-value store system, creating a significant security risk for systems relying on this distributed database. The vulnerability specifically targets the etcd server's API endpoints that process POST requests, which are designed to support the creation of in-order keys through the etcd v3 API. When an attacker crafts a malicious website that automatically submits POST requests to the vulnerable etcd server, they can manipulate the key-value storage by creating new keys with predetermined values. This flaw exploits the fundamental trust model of web applications where user browsers automatically submit requests without explicit user confirmation, making it particularly dangerous in environments where etcd servers are exposed to untrusted networks or where users might inadvertently visit malicious sites. The vulnerability stems from the server's lack of proper CSRF protection mechanisms, particularly around the POST operations that enable the creation of new keys in the etcd datastore.
The technical implementation of this vulnerability leverages the etcd v3 API's POST functionality to create new keys with specific values, bypassing normal access controls and authentication mechanisms. While the PUT operation used for key modification is inherently safer due to its nature of requiring explicit key names and values, the POST operation used for creating new keys in-order allows attackers to submit crafted requests that can modify the database state. The attack vector involves embedding malicious HTML forms or JavaScript code within a compromised website that automatically submits POST requests to the etcd server's API endpoints. These requests can create new keys with values chosen by the attacker, potentially leading to data corruption, unauthorized modifications, or even complete database compromise. The vulnerability is particularly concerning because it allows attackers to perform operations that would normally require legitimate authentication, as the POST requests can be automatically generated and submitted by malicious web pages without user interaction. This represents a violation of the principle of least privilege and demonstrates how improper API design can create security weaknesses even in systems that implement authentication controls.
The operational impact of this vulnerability extends beyond simple data modification, potentially affecting the integrity and availability of distributed systems that depend on etcd for configuration management and service discovery. When an attacker successfully exploits this CSRF flaw, they can manipulate the etcd datastore to redirect service traffic, modify critical configuration parameters, or inject malicious data that could cause cascading failures across the entire system. The vulnerability affects systems where etcd servers are exposed to public networks or where users might browse untrusted websites, as the attack requires no special privileges beyond access to a compromised website. Organizations relying on etcd for critical infrastructure components such as container orchestration systems, microservices architectures, or cloud-native applications face significant risk from this vulnerability. The potential for denial of service through key manipulation, combined with the ability to alter configuration data, creates a multi-faceted threat that can impact system availability, performance, and data integrity. The vulnerability also highlights the importance of proper input validation and CSRF protection mechanisms in distributed systems, as the flaw exists in the core API handling rather than in application-level security controls.
Mitigation strategies for this vulnerability primarily involve upgrading to etcd versions that address the CSRF issues, specifically those released after the vulnerability disclosure. Organizations should implement proper CSRF protection mechanisms at the application level, including the use of anti-CSRF tokens in all state-changing operations and the implementation of strict origin validation for API requests. Network-level protections such as firewalls and access control lists should be implemented to restrict direct access to etcd servers from untrusted networks, ensuring that only authorized clients can submit requests to the API endpoints. Additionally, organizations should consider implementing monitoring and alerting systems that can detect unusual patterns of key creation or modification that might indicate CSRF attacks. The implementation of proper authentication and authorization controls, combined with regular security audits of etcd configurations, can help prevent exploitation of this vulnerability. Security teams should also conduct regular penetration testing to identify potential CSRF vulnerabilities in their etcd deployments and ensure that all API endpoints properly validate request sources and implement appropriate protection mechanisms. This vulnerability serves as a reminder of the critical importance of proper API security design and the need for comprehensive security controls in distributed systems. The flaw aligns with CWE-352, which specifically addresses Cross-Site Request Forgery vulnerabilities, and demonstrates how CSRF protections must be implemented consistently across all API endpoints rather than relying on implicit security measures. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and data manipulation, emphasizing the need for robust security controls in distributed database systems.