medium
6
CWE
755
Advisory Published
Updated

CVE-2020-25602

First published: Wed Sep 23 2020(Updated: )

An issue was discovered in Xen through 4.14.x. An x86 PV guest can trigger a host OS crash when handling guest access to MSR_MISC_ENABLE. When a guest accesses certain Model Specific Registers, Xen first reads the value from hardware to use as the basis for auditing the guest access. For the MISC_ENABLE MSR, which is an Intel specific MSR, this MSR read is performed without error handling for a #GP fault, which is the consequence of trying to read this MSR on non-Intel hardware. A buggy or malicious PV guest administrator can crash Xen, resulting in a host Denial of Service. Only x86 systems are vulnerable. ARM systems are not vulnerable. Only Xen versions 4.11 and onwards are vulnerable. 4.10 and earlier are not vulnerable. Only x86 systems that do not implement the MISC_ENABLE MSR (0x1a0) are vulnerable. AMD and Hygon systems do not implement this MSR and are vulnerable. Intel systems do implement this MSR and are not vulnerable. Other manufacturers have not been checked. Only x86 PV guests can exploit the vulnerability. x86 HVM/PVH guests cannot exploit the vulnerability.

Credit: cve@mitre.org cve@mitre.org

Affected SoftwareAffected VersionHow to fix
Xen Xen>=4.11.0<=4.14.0
Fedoraproject Fedora=31
Fedoraproject Fedora=32
Fedoraproject Fedora=33
Debian Debian Linux=10.0
openSUSE Leap=15.2
debian/xen
4.14.6-1
4.14.5+94-ge49571868d-1
4.17.3+10-g091466ba55-1~deb12u1
4.17.5+23-ga4e5191dc0-1
4.17.3+36-g54dacb5c02-1
4.19.1-1

Remedy

https://xenbits.xen.org/xsa/advisory-333.html

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Reference Links

Frequently Asked Questions

  • What is the vulnerability ID of this issue?

    The vulnerability ID of this issue is CVE-2020-25602.

  • What is the affected software?

    The affected software is Xen through 4.14.x.

  • How can an x86 PV guest trigger a host OS crash?

    An x86 PV guest can trigger a host OS crash when handling guest access to MSR_MISC_ENABLE.

  • How does Xen handle guest access to Model Specific Registers?

    Xen first reads the value from hardware to use as the basis for auditing the guest access.

  • Where can I find more information about this vulnerability?

    You can find more information about this vulnerability on the Xen Project website and the Fedora mailing list.

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