The xenlight library (libxl) in Xen 4.0.x through 4.2.x, when IOMMU is disabled, provides access to a busmastering-capable PCI passthrough device before the IOMMU setup is complete, which allows local HVM guest domains to gain privileges or cause a denial of service via a DMA instruction.
CVSS Severity (version 2.0):
Impact Subscore: 10.0
Exploitability Subscore: 2.5
CVSS Version 2 Metrics:
Access Vector: Local network exploitable
Access Complexity: High
Authentication: Required to exploit
Impact Type: Allows unauthorized disclosure of information; Allows unauthorized modification; Allows disruption of service
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[oss-security] 20130910 Re: Xen Security Advisory 61 - libxl partially sets up HVM passthrough even with disabled iommu
[Xen-devel] 20130701 [PATCH] libxl: suppress device assignment to HVM guest when there is no IOMMU