Xen up to 4.13.x HVM Guest resource consumption

Summaryinfo

A vulnerability described as critical has been identified in Xen up to 4.13.x. The impacted element is an unknown function. Such manipulation as part of HVM Guest leads to resource consumption. This vulnerability is documented as CVE-2020-15565. The attack needs to be performed locally. There is not any exploit available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Xen up to 4.13.x (Virtualization Software). Affected by this issue is an unknown code block. The manipulation as part of a HVM Guest leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. Impacted is confidentiality, integrity, and availability. CVE summarizes:

An issue was discovered in Xen through 4.13.x, allowing x86 Intel HVM guest OS users to cause a host OS denial of service or possibly gain privileges because of insufficient cache write-back under VT-d. When page tables are shared between IOMMU and CPU, changes to them require flushing of both TLBs. Furthermore, IOMMUs may be non-coherent, and hence prior to flushing IOMMU TLBs, a CPU cache also needs writing back to memory after changes were made. Such writing back of cached data was missing in particular when splitting large page mappings into smaller granularity ones. A malicious guest may be able to retain read/write DMA access to frames returned to Xen's free pool, and later reused for another purpose. Host crashes (leading to a Denial of Service) and privilege escalation cannot be ruled out. Xen versions from at least 3.2 onwards are affected. Only x86 Intel systems are affected. x86 AMD as well as Arm systems are not affected. Only x86 HVM guests using hardware assisted paging (HAP), having a passed through PCI device assigned, and having page table sharing enabled can leverage the vulnerability. Note that page table sharing will be enabled (by default) only if Xen considers IOMMU and CPU large page size support compatible.

The weakness was released 07/07/2020 (oss-sec). The advisory is shared for download at openwall.com. This vulnerability is handled as CVE-2020-15565 since 07/06/2020. The exploitation is known to be easy. The attack needs to be approached locally. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Entries connected to this vulnerability are available at VDB-157738, VDB-157737, VDB-157735 and VDB-157734. VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

• Virtualization Software

Name

• Xen

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13

License

• open-source

CPE 2.3info

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CPE 2.2info

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Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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