medium
5.5
CWE
787
Advisory Published
Updated

CVE-2020-25600

First published: Wed Sep 23 2020(Updated: )

An issue was discovered in Xen through 4.14.x. Out of bounds event channels are available to 32-bit x86 domains. The so called 2-level event channel model imposes different limits on the number of usable event channels for 32-bit x86 domains vs 64-bit or Arm (either bitness) ones. 32-bit x86 domains can use only 1023 channels, due to limited space in their shared (between guest and Xen) information structure, whereas all other domains can use up to 4095 in this model. The recording of the respective limit during domain initialization, however, has occurred at a time where domains are still deemed to be 64-bit ones, prior to actually honoring respective domain properties. At the point domains get recognized as 32-bit ones, the limit didn't get updated accordingly. Due to this misbehavior in Xen, 32-bit domains (including Domain 0) servicing other domains may observe event channel allocations to succeed when they should really fail. Subsequent use of such event channels would then possibly lead to corruption of other parts of the shared info structure. An unprivileged guest may cause another domain, in particular Domain 0, to misbehave. This may lead to a Denial of Service (DoS) for the entire system. All Xen versions from 4.4 onwards are vulnerable. Xen versions 4.3 and earlier are not vulnerable. Only x86 32-bit domains servicing other domains are vulnerable. Arm systems, as well as x86 64-bit domains, are not vulnerable.

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

Affected SoftwareAffected VersionHow to fix
Xen Xen>=4.4.0<=4.14.0
Fedoraproject Fedora=31
Fedoraproject Fedora=32
Fedoraproject Fedora=33
openSUSE Leap=15.2
Debian Debian Linux=10.0
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

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Reference Links

Frequently Asked Questions

  • What is CVE-2020-25600?

    CVE-2020-25600 is a vulnerability in Xen through 4.14.x that allows out of bounds event channels in 32-bit x86 domains.

  • How does CVE-2020-25600 affect 32-bit x86 domains?

    CVE-2020-25600 imposes different limits on the number of usable event channels for 32-bit x86 domains.

  • What versions of Xen are affected by CVE-2020-25600?

    Versions up to 4.14.x are affected by CVE-2020-25600.

  • How can I fix CVE-2020-25600?

    To fix CVE-2020-25600, update Xen to version 4.11.3+24- or later.

  • Where can I find more information about CVE-2020-25600?

    You can find more information about CVE-2020-25600 on the Xen Project advisory page at https://xenbits.xen.org/xsa/advisory-342.html.

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