Vulnerability identifier: #VU7151

Vulnerability risk: Low

CVSSv3.1: 4.6 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:U/RL:O/RC:C]

CVE-ID: CVE-2017-10920

CWE-ID: CWE-264

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
Xen
Server applications / Virtualization software

Vendor: Xen Project

Description
The vulnerability allows a local attacker to gain elevated privileges.

The weakness exists due to flaws in the mapping and unmapping of grant references. If a grant is mapped with both the GNTMAP_device_map and GNTMAP_host_map flags, but unmapped only with host_map, the device_map portion remains but the page reference counts are lowered as though it had been removed. This bug can be leveraged cause a page's reference counts and type counts to fall to zero while retaining writeable mappings to the page.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Xen: 4.5.0 - 4.8.1

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External links
http://xenbits.xen.org/xsa/advisory-224.html

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.