#VU32431 Permissions, Privileges, and Access Controls in Xen - CVE-2015-2756

Vulnerability identifier: #VU32431

Vulnerability risk: Low

CVSSv4.0: 4.6 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2015-2756

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 non-authenticated attacker to perform a denial of service (DoS) attack.

QEMU, as used in Xen 3.3.x through 4.5.x, does not properly restrict access to PCI command registers, which might allow local HVM guest users to cause a denial of service (non-maskable interrupt and host crash) by disabling the (1) memory or (2) I/O decoding for a PCI Express device and then accessing the device, which triggers an Unsupported Request (UR) response.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Xen: 3.3.0 - 3.3.2

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External links
https://lists.fedoraproject.org/pipermail/package-announce/2015-April/154574.html
https://lists.fedoraproject.org/pipermail/package-announce/2015-April/154579.html
https://lists.fedoraproject.org/pipermail/package-announce/2015-April/155198.html
https://lists.nongnu.org/archive/html/qemu-devel/2015-03/msg06179.html
https://lists.opensuse.org/opensuse-security-announce/2015-04/msg00014.html
https://support.citrix.com/article/CTX201145
https://www.debian.org/security/2015/dsa-3259
https://www.securityfocus.com/bid/72577
https://www.securitytracker.com/id/1031998
https://www.ubuntu.com/usn/USN-2608-1
https://xenbits.xen.org/xsa/advisory-126.html
https://security.gentoo.org/glsa/201504-04
https://support.citrix.com/article/CTX206006

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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.