CVE-2017-17877 in Steam Link
Summary
by MITRE
An issue was discovered in Valve Steam Link build 643. When the SSH daemon is enabled for local development, the device is publicly available via IPv6 TCP port 22 over the internet (with stateless address autoconfiguration) by default, which makes it easier for remote attackers to obtain access by guessing 24 bits of the MAC address and attempting a root login. This can be exploited in conjunction with CVE-2017-17878.
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Analysis
by VulDB Data Team • 01/19/2023
The vulnerability identified as CVE-2017-17877 represents a critical security flaw in Valve Steam Link devices running build 643, where the SSH daemon is enabled by default for local development purposes. This configuration creates an unexpected exposure that extends beyond the intended local network boundaries, making the device accessible over the internet through IPv6 connections. The vulnerability stems from the device's default configuration that enables remote SSH access without proper network segmentation or access controls, creating an attack surface that adversaries can exploit without requiring physical access to the device. The security implications are particularly severe because the SSH service is accessible via IPv6 TCP port 22, which is a standard port for secure shell communications, and this exposure occurs without any authentication barriers for external connections.
The technical exploitation of this vulnerability leverages the device's IPv6 stateless address autoconfiguration capabilities, which automatically generate network addresses for devices on the network. Attackers can exploit this by guessing 24 bits of the MAC address to determine the target device's IPv6 address, then attempt to establish an SSH connection to the root account. This approach significantly reduces the complexity of the attack compared to traditional methods of discovering and accessing SSH services. The vulnerability demonstrates a fundamental flaw in the device's default security posture, where the assumption that local development features should remain isolated within local networks fails to account for the broader internet exposure that IPv6 connectivity can create. The attack vector is particularly concerning because it requires minimal reconnaissance effort and can be automated, making it attractive to both automated scanning tools and targeted attackers.
The operational impact of this vulnerability extends beyond simple unauthorized access to potentially compromise the entire Steam Link device and any connected systems. Once an attacker gains root access, they can modify system configurations, install malicious software, access stored credentials, and potentially use the device as a pivot point for accessing other systems on the network. The vulnerability can be exploited in conjunction with CVE-2017-17878, which suggests that the security flaws are part of a broader pattern of misconfigurations in the device's network security implementation. This interconnected nature of vulnerabilities makes the overall threat more significant, as attackers can chain these exploits together to achieve more extensive compromise than either vulnerability would allow independently. The impact is particularly severe for users who rely on Steam Link devices for gaming or media streaming, as the compromise could lead to unauthorized access to personal data, streaming content, and potentially even control over connected home entertainment systems.
The security implications of this vulnerability align with CWE-284, which addresses improper access control in software systems, and can be mapped to ATT&CK technique T1021.004 for remote services access through SSH. Organizations and users should immediately disable SSH access on Steam Link devices when not actively using it for development purposes, implement proper network segmentation to isolate such devices, and ensure that any remote access is properly secured through VPN connections or other secure tunneling mechanisms. Additionally, regular firmware updates should be applied to ensure that security patches addressing these issues are implemented. The vulnerability highlights the importance of secure default configurations and demonstrates why devices connected to the internet should not expose administrative services by default, even when intended for development use. Network administrators should also implement firewall rules to block external access to SSH ports and monitor for unauthorized SSH connection attempts to identify potential exploitation attempts.