CVE-2017-10664 in QEMU
Summary
by MITRE
qemu-nbd in QEMU (aka Quick Emulator) does not ignore SIGPIPE, which allows remote attackers to cause a denial of service (daemon crash) by disconnecting during a server-to-client reply attempt.
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability identified as CVE-2017-10664 affects the qemu-nbd component within the QEMU virtualization platform, specifically targeting how the daemon handles SIGPIPE signals during network block device operations. This issue resides in the server-side implementation of the Network Block Device protocol where QEMU's nbd server fails to properly ignore SIGPIPE signals that occur when attempting to send data to a disconnected client. The root cause stems from improper signal handling mechanisms that leave the daemon in an unstable state when network interruptions occur during data transmission. When a client disconnects while the server is attempting to reply, the SIGPIPE signal is not properly caught and handled, leading to an abrupt termination of the qemu-nbd process and subsequent denial of service condition. This vulnerability specifically impacts QEMU versions prior to 2.10.0, making it a critical concern for systems running older virtualization infrastructure. The flaw represents a classic signal handling weakness that allows attackers to exploit the daemon's response to network interruptions.
The technical implementation of this vulnerability demonstrates a fundamental flaw in process signal management within the QEMU nbd server component. During normal operation, the qemu-nbd daemon establishes network connections to serve block device requests from remote clients. When a client disconnects unexpectedly while the server is in the process of sending a reply, the underlying write operation generates a SIGPIPE signal that terminates the process without proper cleanup. This behavior violates standard practices for robust network service implementation where signal handling should be configured to prevent daemon crashes from network interruptions. The vulnerability specifically manifests when the server attempts to write data to a socket that has already been closed by the remote client, causing the write operation to fail and trigger SIGPIPE. This issue is classified under CWE-403: "Unprotected Resource Access" and aligns with ATT&CK technique T1499.004 for Network Denial of Service attacks. The daemon's failure to implement proper signal masking or handling for SIGPIPE creates an exploitable condition that remote attackers can leverage through network disruption techniques.
The operational impact of CVE-2017-10664 extends beyond simple service interruption to potentially compromise virtual machine availability and system stability in virtualized environments. When exploited, this vulnerability allows remote attackers to cause immediate daemon crashes, effectively taking the affected QEMU nbd service offline and preventing legitimate clients from accessing virtual block devices. In production virtualization environments, this can result in significant service disruption as multiple virtual machines may rely on the same nbd server instance for storage access. The vulnerability is particularly concerning in cloud computing and containerized environments where QEMU nbd services are commonly deployed for storage provisioning and virtual machine management. Attackers can repeatedly exploit this condition to maintain persistent denial of service, potentially causing cascading failures in systems that depend on continuous storage availability. The impact is amplified in scenarios where multiple virtual machines share the same underlying storage infrastructure, as a single exploitation event can affect numerous guest operating systems simultaneously. This vulnerability also represents a potential vector for more sophisticated attacks that could leverage the service disruption to gain additional system access or escalate privileges.
Mitigation strategies for CVE-2017-10664 focus primarily on upgrading to patched versions of QEMU where the signal handling has been corrected to properly ignore SIGPIPE signals during network operations. System administrators should immediately update their QEMU installations to version 2.10.0 or later where this vulnerability has been addressed through proper signal management implementation. Additionally, network-level protections such as firewall rules and connection monitoring can help detect and prevent exploitation attempts by limiting access to vulnerable nbd services. Implementing proper process monitoring and automatic restart mechanisms for qemu-nbd daemons can help maintain service availability even if individual instances are compromised. Organizations should also consider implementing network segmentation to isolate nbd services from untrusted networks and deploy intrusion detection systems to monitor for unusual network disconnection patterns that may indicate exploitation attempts. The fix in patched versions typically involves implementing proper signal masking for SIGPIPE during write operations and ensuring that the daemon continues to operate normally even when individual client connections are terminated unexpectedly. Security teams should also conduct regular vulnerability assessments to identify other potentially unpatched instances of QEMU in their environment and ensure that all virtualization infrastructure components are kept up to date with security patches.