CVE-2019-19755 in ethOS
Summary
by MITRE • 04/30/2024
ethOS through 1.3.3 ships with SSH host keys baked into the installation image, which allows man-in-the-middle attacks and makes identification of all public IPv4 nodes trivial with Shodan.io. NOTE: as of 2019-12-01, the vendor indicated that they plan to fix this.
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Analysis
by VulDB Data Team • 08/15/2024
The vulnerability described in CVE-2019-19755 represents a critical security flaw in ethOS versions 1.3.3 and earlier, where the system ships with hardcoded SSH host keys embedded within its installation image. This fundamental design decision creates a severe exposure that undermines the core security principles of secure remote access protocols. The presence of identical cryptographic keys across all installations means that any attacker who discovers one ethOS device can easily compromise others by exploiting this shared cryptographic identity. This vulnerability directly violates security best practices outlined in the National Institute of Standards and Technology guidelines for secure system configuration and authentication protocols.
The technical implementation of this flaw stems from the improper handling of cryptographic key management within the ethOS distribution. When SSH host keys are baked into the installation image, they become static and predictable across all instances of the software, eliminating the unique identification properties that cryptographic keys should provide. This design flaw enables attackers to perform man-in-the-middle attacks with minimal effort since the host key fingerprint remains consistent across all systems. The vulnerability specifically targets the SSH protocol's trust model, where the host key serves as a critical authentication mechanism to verify the identity of the remote system. According to CWE-310, this represents a cryptographic weakness that exposes systems to various forms of attack including authentication bypass and session hijacking. The attack surface is significantly expanded as demonstrated by the ease with which security researchers can identify all public IPv4 nodes running affected versions through services like Shodan.io, which aggregates and indexes exposed SSH services globally.
The operational impact of this vulnerability extends far beyond simple authentication concerns, creating a comprehensive security risk that affects network infrastructure and device management. Organizations deploying ethOS systems face the immediate risk of unauthorized access to their network resources, as attackers can exploit the predictable host keys to establish malicious connections without proper authentication. This vulnerability enables several attack patterns documented in the MITRE ATT&CK framework, particularly those related to credential access and lateral movement. The exposure of all public nodes through Shodan.io creates a massive attack surface that allows threat actors to systematically scan for and target vulnerable ethOS installations. Additionally, the flaw compromises the integrity of the SSH protocol's security model, potentially allowing attackers to perform session hijacking, data interception, and privilege escalation attacks against the affected systems.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements to prevent similar issues. The primary solution involves updating to a patched version of ethOS where unique host keys are generated during the installation process or at first boot, ensuring each system maintains a distinct cryptographic identity. Organizations should implement network segmentation and firewall rules to restrict SSH access to trusted networks only, while also deploying intrusion detection systems to monitor for unauthorized SSH connections. The remediation process should include generating new SSH host keys on all affected systems and updating any configurations that rely on the old host key fingerprints. Security teams should also conduct comprehensive network scans to identify all instances of the vulnerable software and ensure proper key rotation procedures are implemented. This vulnerability highlights the importance of following secure coding practices and proper key management as outlined in industry standards including NIST SP 800-57 for cryptographic key management and OWASP secure coding guidelines for preventing cryptographic weaknesses in software implementations.