CVE-2018-19364 in QEMU
Summary
by MITRE
hw/9pfs/cofile.c and hw/9pfs/9p.c in QEMU can modify an fid path while it is being accessed by a second thread, leading to (for example) a use-after-free outcome.
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2018-19364 resides within the QEMU virtualization software, specifically in the 9p filesystem implementation components located in hw/9pfs/cofile.c and hw/9pfs/9p.c. This flaw represents a classic race condition scenario that occurs when multiple threads attempt to access shared resources without proper synchronization mechanisms. The 9p protocol implementation in QEMU enables communication between the guest operating system and the host filesystem through a virtualized interface, making it a critical component for virtual machine functionality and security.
The technical root cause of this vulnerability stems from insufficient thread synchronization when handling file identifiers or fids within the 9p filesystem backend. When one thread modifies the path associated with a file identifier while another thread is actively accessing that same fid, the system can experience unpredictable behavior including memory corruption and use-after-free conditions. This particular flaw allows for a scenario where a thread might free memory associated with a file path while another thread is still referencing that memory location, creating a potential avenue for arbitrary code execution or system instability. The vulnerability manifests as a race condition that violates fundamental concurrency control principles and can be exploited by malicious actors within the guest operating system.
The operational impact of this vulnerability extends beyond simple system crashes or instability, as it provides potential attackers with opportunities to escalate privileges and execute arbitrary code within the virtualized environment. When exploited successfully, this race condition could allow a guest operating system user to gain access to the host system or compromise the integrity of other virtual machines running on the same host. The implications are particularly severe in cloud computing environments where multiple tenants share the same physical infrastructure, as this vulnerability could enable cross-tenant attacks and privilege escalation across isolated virtual environments. The use-after-free condition creates a memory corruption vulnerability that can be leveraged for exploitation techniques targeting the underlying QEMU process.
Mitigation strategies for CVE-2018-19364 primarily involve applying the official patches released by the QEMU development team, which typically implement proper locking mechanisms and synchronization primitives to prevent concurrent access to shared fid structures. System administrators should also consider implementing additional security measures such as restricting guest operating system privileges, disabling unnecessary 9p filesystem exports, and monitoring for suspicious activity patterns that might indicate exploitation attempts. Organizations running QEMU-based virtualization environments should conduct thorough vulnerability assessments and ensure all virtual machines are updated to versions that contain the relevant fixes. The vulnerability aligns with CWE-362, which describes race conditions in concurrent programming, and could potentially map to ATT&CK technique T1059 for execution through guest operating systems, as well as T1078 for privilege escalation in virtualized environments. Regular security audits and proper virtualization security hardening practices are essential for preventing exploitation of this class of vulnerabilities in production environments.