CVE-2016-7777

Description

Xen 4.7.x and earlier does not properly honor CR0.TS and CR0.EM, which allows local x86 HVM guest OS users to read or modify FPU, MMX, or XMM register state information belonging to arbitrary tasks on the guest by modifying an instruction while the hypervisor is preparing to emulate it.

CVSS Metrics

• v3.0•MEDIUM•Score: 6.3CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
• v2.0•LOW•Score: 3.3AV:L/AC:M/Au:N/C:P/I:P/A:N

EPSS Trends

Current EPSS score: 0.12%• Percentile: 31%

Techniques & Countermeasures

• CWE-362•Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

  The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Systems

• xen•xen

  ≤ 4.7.0

References (5)

• https://support.citrix.com/article/CTX217363
• http://xenbits.xen.org/xsa/advisory-190.html
• http://www.securityfocus.com/bid/93344
• https://security.gentoo.org/glsa/201611-09
• http://www.securitytracker.com/id/1036942