CVE-2018-19489 in QEMU
Summary
by MITRE
v9fs_wstat in hw/9pfs/9p.c in QEMU allows guest OS users to cause a denial of service (crash) because of a race condition during file renaming.
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2018-19489 resides within the QEMU virtualization platform's 9p filesystem implementation, specifically in the v9fs_wstat function located in hw/9pfs/9p.c. This flaw represents a critical race condition that occurs during file renaming operations when a guest operating system attempts to modify file attributes through the 9p protocol. The 9p protocol serves as a network filesystem interface that enables communication between guest and host systems, making it a fundamental component in virtualized environments where shared filesystems are utilized.
The technical nature of this vulnerability stems from improper synchronization mechanisms during concurrent file operations. When multiple processes or threads attempt to rename or modify file attributes simultaneously, the v9fs_wstat function fails to properly handle the race condition between the file deletion and creation phases of the rename operation. This improper handling leads to memory corruption and subsequent system crashes that can be exploited by unprivileged guest users to cause denial of service conditions. The vulnerability is particularly concerning because it allows a guest operating system user to trigger a crash that affects the entire virtual machine, potentially leading to system instability and service disruption.
From an operational impact perspective, this vulnerability poses significant risks to virtualized environments where multiple guest operating systems share host resources. The denial of service condition can result in complete virtual machine crashes, requiring manual intervention for recovery and potentially causing data loss or service interruptions for dependent applications. The vulnerability affects QEMU versions prior to 2.12.0, making it a widespread concern for organizations maintaining older virtualization infrastructure. Security researchers have classified this issue under CWE-362, which specifically addresses race conditions in software implementations, and it aligns with ATT&CK technique T1499.001 for resource exhaustion attacks that can be leveraged to cause denial of service conditions.
Mitigation strategies for CVE-2018-19489 primarily involve upgrading QEMU to version 2.12.0 or later, which includes proper synchronization mechanisms to prevent the race condition. Organizations should also implement network segmentation to limit guest access to critical virtualization components and consider disabling 9p filesystem sharing when it is not essential for operations. Additional protective measures include monitoring virtual machine logs for unusual file operation patterns and implementing intrusion detection systems that can identify potential exploitation attempts. System administrators should conduct regular vulnerability assessments of their virtualization infrastructure to identify and remediate similar race condition vulnerabilities that may exist in other components of their virtualization stack.