CVE-2017-15588 in Xen
Summary
by MITRE
An issue was discovered in Xen through 4.9.x allowing x86 PV guest OS users to execute arbitrary code on the host OS because of a race condition that can cause a stale TLB entry.
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Analysis
by VulDB Data Team • 01/04/2023
The vulnerability identified as CVE-2017-15588 represents a critical security flaw in the Xen hypervisor affecting versions 4.9.x and earlier. This issue resides within the x86 paravirtualized guest operating system implementation and creates a pathway for malicious guest users to escalate privileges and execute arbitrary code on the host system. The vulnerability stems from a fundamental race condition within the memory management subsystem that governs translation lookaside buffer operations, which are essential for virtual memory management in virtualized environments.
The technical flaw manifests through a race condition that occurs during the handling of memory translations within the hypervisor's memory management layer. When a paravirtualized guest operating system performs memory operations, the hypervisor maintains translation lookaside buffer entries to map guest virtual addresses to host physical addresses. The race condition arises when multiple concurrent operations attempt to modify or invalidate these TLB entries without proper synchronization mechanisms. This timing issue can result in stale TLB entries remaining in the hypervisor's memory management tables even after the corresponding memory mappings have been changed or invalidated by legitimate operations. The stale entries essentially create a window where guest users can manipulate memory access patterns to exploit the outdated translation information.
The operational impact of this vulnerability extends beyond simple privilege escalation, creating a serious threat to the integrity and security of the entire virtualized infrastructure. Attackers with access to a paravirtualized guest operating system can leverage this flaw to execute arbitrary code with the privileges of the host hypervisor itself, effectively compromising the security isolation that virtualization is designed to provide. This capability enables attackers to access sensitive data, modify system configurations, or even establish persistent backdoors within the host environment. The vulnerability is particularly dangerous because it operates at a low level within the hypervisor, making detection and prevention challenging. The race condition nature of the flaw means that exploitation may not be consistently reproducible, but once successful, it provides complete control over the host system.
Mitigation strategies for CVE-2017-15588 focus primarily on applying the official patches released by the Xen project, which address the underlying race condition through improved synchronization mechanisms and proper TLB entry management. Organizations should prioritize updating their Xen hypervisor installations to versions 4.10.0 or later, where the vulnerability has been fully remediated. Additionally, implementing runtime monitoring for unusual memory access patterns and TLB operations can help detect potential exploitation attempts. System administrators should also consider implementing additional security controls such as disabling unnecessary paravirtualized features, restricting guest user privileges, and maintaining strict access controls for virtual machine management interfaces. This vulnerability aligns with CWE-362, which describes a race condition in software design, and maps to ATT&CK technique T1055.011, which covers privilege escalation through hypervisor manipulation. The flaw demonstrates how seemingly minor synchronization issues in low-level system components can create catastrophic security implications in virtualized environments, emphasizing the critical importance of rigorous security testing for hypervisor implementations.