CVE-2017-14431 in Xen
Summary
by MITRE
Memory leak in Xen 3.3 through 4.8.x allows guest OS users to cause a denial of service (ARM or x86 AMD host OS memory consumption) by continually rebooting, because certain cleanup is skipped if no pass-through device was ever assigned, aka XSA-207.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/15/2019
This vulnerability represents a critical memory management flaw in the Xen hypervisor affecting versions 3.3 through 4.8.x across both ARM and x86 AMD architectures. The issue stems from improper resource cleanup procedures within the hypervisor's memory management subsystem, specifically when handling guest operating system reboots. When a guest OS performs a reboot operation without having previously assigned any pass-through devices, the hypervisor fails to execute essential cleanup routines that would normally release allocated memory resources back to the host system. This oversight creates a persistent memory leak that accumulates over time, as each reboot operation leaves behind fragmented memory segments that cannot be properly reclaimed by the host operating system.
The technical implementation of this vulnerability resides in the hypervisor's device assignment and memory deallocation logic. According to CWE-401, this represents a classic memory leak condition where allocated memory resources are not properly freed, leading to gradual resource exhaustion. The flaw manifests when the hypervisor's cleanup code path is bypassed due to the absence of pass-through device assignments, creating a conditional execution path that fails to release memory structures associated with guest memory mappings and device context information. This behavior violates fundamental memory management principles and creates a persistent state where host memory consumption grows indefinitely with each guest reboot operation.
The operational impact of CVE-2017-14431 enables a straightforward denial of service attack that can be executed by any authenticated guest OS user with minimal technical expertise. Attackers can repeatedly reboot guest virtual machines to gradually consume host system memory resources until system performance degrades significantly or complete system crashes occur. This vulnerability specifically affects the ARM and x86 AMD architectures, making it particularly dangerous in virtualized environments where multiple guests may be running simultaneously. The cumulative nature of the memory leak means that even a single malicious guest can eventually exhaust host resources, potentially affecting all virtual machines sharing the same physical host. From an attack technique perspective, this vulnerability aligns with ATT&CK tactic TA0040 (Resource Hijacking) and technique T1499.001 (Network Denial of Service) when considering the broader impact on system availability.
Mitigation strategies for this vulnerability require immediate patching of affected Xen hypervisor versions to address the memory cleanup logic. System administrators should prioritize updating to versions 4.9.0 or later where the memory leak has been corrected through proper conditional cleanup routines. Additionally, monitoring systems should be implemented to track memory consumption patterns on hypervisor hosts and establish automated alerts when memory usage exceeds predefined thresholds. Virtualization administrators should also implement guest resource limits and monitoring to prevent any single guest from consuming excessive host resources. The fix typically involves modifying the hypervisor's device assignment code to ensure that cleanup routines execute consistently regardless of whether pass-through devices were previously assigned, thereby preventing the accumulation of unreleased memory segments that characterize this particular vulnerability.