Critical InputPlumber Vulnerabilities Expose Linux Systems to UI Injection and Denial-of-Service Attacks
Recent discoveries have unveiled critical vulnerabilities in InputPlumber, a Linux utility integral to SteamOS, which could permit attackers to inject unauthorized user interface (UI) inputs and induce denial-of-service (DoS) conditions on affected systems. These vulnerabilities, identified as CVE-2025-66005 and CVE-2025-14338, impact InputPlumber versions prior to v0.69.0 and are primarily due to insufficient D-Bus authorization mechanisms.
Understanding InputPlumber and Its Role
InputPlumber is a utility designed to amalgamate multiple Linux input devices into virtual input devices, facilitating seamless user interactions. Operating with full root privileges, it plays a pivotal role in managing input devices within SteamOS environments. However, the elevated privileges also mean that any security flaws within InputPlumber can have significant repercussions.
Details of the Vulnerabilities
The vulnerabilities stem from inadequate authorization checks within InputPlumber’s D-Bus interface, allowing any user, including those with minimal privileges, to access its services without proper authentication.
– CVE-2025-66005: This vulnerability arises from missing authorization in the D-Bus interface in versions before v0.63.0. Exploitation can lead to denial-of-service, information leakage, and potential privilege escalation.
– CVE-2025-14338: Present in versions before v0.69.0, this flaw is due to disabled Polkit authentication combined with an authorization race condition. Attackers can exploit this to cause denial-of-service, leak sensitive information, and escalate privileges.
Potential Exploitation Scenarios
Attackers with access to these vulnerabilities can exploit them in several ways:
1. UI Input Injection: By creating virtual keyboard devices, malicious actors can inject keystrokes into active user sessions. This could lead to unauthorized actions being performed, potentially resulting in arbitrary code execution within the context of the logged-in user.
2. Denial-of-Service (DoS): The `CreateCompositeDevice` method in InputPlumber accepts file paths from clients. Attackers can exploit this by passing special files, such as `/dev/zero`, leading to memory exhaustion and system crashes.
3. Information Disclosure: The same method can be manipulated to test for the existence of files and leak sensitive information from files that are typically inaccessible to low-privilege users, such as `/root/.bash_history`.
Affected Systems
The primary systems at risk are Linux gaming platforms utilizing InputPlumber, notably those running SteamOS. Given the widespread use of SteamOS among gaming enthusiasts, the potential impact of these vulnerabilities is substantial.
Mitigation Measures
To address these vulnerabilities, the following steps are recommended:
1. Update InputPlumber: Valve has released SteamOS 3.7.20, which includes the patched InputPlumber v0.69.0. Users should update to this version or later to mitigate the identified risks.
2. Implement Proper Authentication: Developers have transitioned to using Polkit authentication, enabling authorization by default and applying systemd hardening measures. System administrators should ensure these configurations are correctly implemented.
3. Monitor for Unusual Activity: Regularly review system logs for any signs of unauthorized access or unusual behavior that could indicate exploitation attempts.
Coordinated Disclosure and Response
The vulnerabilities were identified by SUSE security researchers, who coordinated with InputPlumber developers to ensure that fixes were available prior to public disclosure. This collaborative approach underscores the importance of timely communication and action in the cybersecurity community to protect users from potential threats.
Conclusion
The discovery of these critical vulnerabilities in InputPlumber highlights the ongoing challenges in securing system utilities that operate with elevated privileges. Users and administrators are urged to promptly update their systems and implement the recommended security measures to safeguard against potential exploits.
