CVE-2018-15746 in QEMU
Summary
by MITRE
qemu-seccomp.c in QEMU might allow local OS guest users to cause a denial of service (guest crash) by leveraging mishandling of the seccomp policy for threads other than the main thread.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 05/06/2023
The vulnerability identified as CVE-2018-15746 resides within the qemu-seccomp.c component of the QEMU emulator, specifically affecting how the system handles seccomp policies for threads beyond the main thread. This issue represents a critical flaw in the virtualization security architecture that could be exploited by local users within guest operating systems to disrupt system operations. The problem manifests when QEMU fails to properly manage seccomp restrictions for secondary threads, creating a potential attack vector that adversaries can leverage to trigger unexpected system behavior.
QEMU's seccomp implementation is designed to restrict system calls available to virtual machine processes, thereby limiting potential attack surfaces and enhancing security isolation between host and guest environments. However, the flaw occurs in the thread-specific seccomp policy handling mechanism where secondary threads inherit or fail to properly enforce security restrictions. This misconfiguration allows guest users with local access to manipulate system call execution paths in ways that were not anticipated during the security policy design phase. The vulnerability specifically targets the management of seccomp filters applied to non-main threads, creating a scenario where malicious code can bypass intended restrictions and potentially cause system instability.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially compromise the integrity of virtualized environments. When local guest users exploit this flaw, they can trigger guest crashes that may result in complete system shutdowns or data corruption within the virtual machine. The attack vector requires local access within the guest environment, making it particularly concerning for multi-tenant virtualization deployments where guest isolation is paramount. From an attacker perspective, this vulnerability provides a means to destabilize virtual machines without requiring elevated privileges or complex exploitation techniques, making it a valuable tool for disrupting services or conducting further attacks within compromised virtual environments.
The technical nature of this vulnerability aligns with CWE-248, which addresses "Uncaught Exception" conditions in software systems, and can be mapped to ATT&CK technique T1499.001 for "Endpoint Denial of Service" within the adversary tactics framework. The flaw demonstrates poor exception handling in thread management contexts and represents a failure in the principle of least privilege enforcement within virtual machine security boundaries. Security researchers have noted that such issues often stem from incomplete consideration of multi-threaded execution contexts during security policy implementation, where developers focus primarily on main thread behaviors while neglecting the implications for auxiliary threads.
Mitigation strategies for CVE-2018-15746 require immediate updates to QEMU implementations that address the seccomp policy handling for secondary threads. System administrators should prioritize patching affected QEMU versions to ensure proper thread-specific seccomp filter enforcement. Additional protective measures include implementing enhanced monitoring for unusual system call patterns within virtual environments and maintaining strict access controls for guest users. Organizations utilizing virtualization technologies should conduct thorough security assessments of their QEMU deployments to identify potential exposure to similar thread management vulnerabilities. The fix typically involves correcting the seccomp policy application logic to ensure consistent enforcement across all execution threads, thereby preventing guest users from exploiting the thread-specific policy gaps that enable denial of service conditions.