medium
5.5
CWE
74
Advisory Published
Updated

CVE-2020-25596

First published: Wed Sep 23 2020(Updated: )

An issue was discovered in Xen through 4.14.x. x86 PV guest kernels can experience denial of service via SYSENTER. The SYSENTER instruction leaves various state sanitization activities to software. One of Xen's sanitization paths injects a #GP fault, and incorrectly delivers it twice to the guest. This causes the guest kernel to observe a kernel-privilege #GP fault (typically fatal) rather than a user-privilege #GP fault (usually converted into SIGSEGV/etc.). Malicious or buggy userspace can crash the guest kernel, resulting in a VM Denial of Service. All versions of Xen from 3.2 onwards are vulnerable. Only x86 systems are vulnerable. ARM platforms are not vulnerable. Only x86 systems that support the SYSENTER instruction in 64bit mode are vulnerable. This is believed to be Intel, Centaur, and Shanghai CPUs. AMD and Hygon CPUs are not believed to be vulnerable. Only x86 PV guests can exploit the vulnerability. x86 PVH / HVM guests cannot exploit the vulnerability.

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

Affected SoftwareAffected VersionHow to fix
Xen Xen>=3.2.0<=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
4.17.3+36-g54dacb5c02-1

Remedy

https://xenbits.xen.org/xsa/advisory-339.html

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Reference Links

Frequently Asked Questions

  • What is the vulnerability ID for this issue?

    The vulnerability ID for this issue is CVE-2020-25596.

  • What is the severity of CVE-2020-25596?

    The severity of CVE-2020-25596 is not specified in the provided information.

  • How can x86 PV guest kernels be affected by CVE-2020-25596?

    x86 PV guest kernels can experience denial of service via SYSENTER due to CVE-2020-25596.

  • What is the remediation for CVE-2020-25596?

    The remediation for CVE-2020-25596 is to update the Xen package to version 4.11.3+24- or higher.

  • Where can I find more information about CVE-2020-25596?

    You can find more information about CVE-2020-25596 at the following references: [Reference 1](https://xenbits.xen.org/xsa/advisory-339.html), [Reference 2](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4JRXMKEMQRQYWYEPHVBIWUEAVQ3LU4FN/), [Reference 3](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DA633Y3G5KX7MKRN4PFEGM3IVTJMBEOM/)

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