CVE-2020-25652 in spice-vdagentd
Summary
by MITRE • 11/26/2020
A flaw was found in the spice-vdagentd daemon, where it did not properly handle client connections that can be established via the UNIX domain socket in `/run/spice-vdagentd/spice-vdagent-sock`. Any unprivileged local guest user could use this flaw to prevent legitimate agents from connecting to the spice-vdagentd daemon, resulting in a denial of service. The highest threat from this vulnerability is to system availability. This flaw affects spice-vdagent versions 0.20 and prior.
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Analysis
by VulDB Data Team • 05/16/2025
The spice-vdagentd daemon represents a critical component in virtualized environments where it facilitates communication between guest operating systems and host systems through the SPICE (SPICE Protocol) framework. This daemon operates with elevated privileges and manages connections through a UNIX domain socket located at /run/spice-vdagentd/spice-vdagent-sock, making it a potential attack surface for local privilege escalation and denial of service attacks. The vulnerability stems from improper handling of client connections, specifically failing to validate or properly manage connection attempts from unauthorized local users who can establish malicious connections to the daemon.
The technical flaw manifests in the daemon's insufficient input validation and connection management mechanisms, allowing any unprivileged local user to exploit the UNIX domain socket interface to disrupt legitimate agent communications. This weakness enables attackers to establish persistent connections that prevent legitimate spice-vdagent processes from connecting to the daemon, effectively creating a denial of service condition that impacts the entire virtualization environment. The vulnerability operates at the system level where local users can leverage their existing privileges to manipulate daemon behavior without requiring additional elevation. The flaw is particularly concerning because it exists within the daemon's core connection handling logic, making it difficult to detect and mitigate without proper access controls and connection validation.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the integrity of virtualized environments where spice-vdagent serves as a critical communication bridge. When legitimate agents cannot establish connections, virtual desktop environments may become unresponsive or fail to function correctly, affecting user productivity and system availability. The threat level is categorized as high due to the ease of exploitation and the significant impact on system availability, particularly in enterprise environments where virtualization platforms are heavily relied upon for desktop delivery and remote access services. This vulnerability affects all versions of spice-vdagent up to and including version 0.20, making it widespread across many virtualization deployments.
Mitigation strategies should focus on implementing proper access controls for the UNIX domain socket, including restricting permissions and ensuring only authorized processes can establish connections to the daemon. System administrators should update to spice-vdagent versions 0.21 or later where this vulnerability has been patched through improved connection validation and proper resource management. The fix typically involves implementing stricter authentication mechanisms and connection handling protocols that prevent unauthorized users from establishing disruptive connections. Additionally, monitoring and logging of connection attempts to the UNIX domain socket should be implemented to detect potential exploitation attempts and maintain audit trails for security investigations. This vulnerability aligns with CWE-284 (Improper Access Control) and can be mapped to ATT&CK technique T1068 (Exploitation for Privilege Escalation) when exploited by local users to disrupt system services and maintain persistent access to compromised virtual environments.