high
7.8
CWE
362
Advisory Published
Updated

CVE-2020-11739: Race Condition

First published: Tue Apr 14 2020(Updated: )

An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded.

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

Affected SoftwareAffected VersionHow to fix
Xen Xen<=4.13.0
Xen Xen=4.13.0-rc1
Xen Xen=4.13.0-rc2
Fedoraproject Fedora=30
Fedoraproject Fedora=31
Fedoraproject Fedora=32
Debian Debian Linux=10.0
openSUSE Leap=15.1
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

http://www.openwall.com/lists/oss-security/2020/04/14/2

Remedy

http://xenbits.xen.org/xsa/advisory-314.html

Remedy

https://xenbits.xen.org/xsa/advisory-314.html

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Reference Links

Frequently Asked Questions

  • What is CVE-2020-11739?

    CVE-2020-11739 is a vulnerability discovered in Xen through 4.13.x that allows guest OS users to cause a denial of service or possibly gain privileges due to missing memory barriers.

  • How can the CVE-2020-11739 vulnerability be exploited?

    The CVE-2020-11739 vulnerability can be exploited by guest OS users to cause a denial of service or potentially gain privileges by taking advantage of the missing memory barriers in read-write unlock paths.

  • Which software versions are affected by CVE-2020-11739?

    Software versions up to and including Xen 4.13.x are affected by CVE-2020-11739.

  • How can I mitigate the CVE-2020-11739 vulnerability?

    To mitigate the CVE-2020-11739 vulnerability, update Xen to version 4.11.3+24- or later on Ubuntu systems, or version 4.11.4+107-gef32c7afa2-1, 4.14.5+94-ge49571868d-1, 4.17.1+2-gb773c48e36-1, or 4.17.2-1 on Debian systems.

  • Where can I find more information about CVE-2020-11739?

    More information about CVE-2020-11739 can be found on the Xen Project website (xenbits.xen.org/xsa/advisory-314.html) and the OpenWall OSS Security mailing list (www.openwall.com/lists/oss-security/2020/04/14/2).

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