high
7.8
CWE
362
Advisory Published
Updated

CVE-2021-28701: Race Condition

First published: Wed Sep 08 2021(Updated: )

Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with a guest for its entire lifetime. Grant table v2 status pages, however, are de-allocated when a guest switches (back) from v2 to v1. Freeing such pages requires that the hypervisor enforce that no parallel request can result in the addition of a mapping of such a page to a guest. That enforcement was missing, allowing guests to retain access to pages that were freed and perhaps re-used for other purposes. Unfortunately, when XSA-379 was being prepared, this similar issue was not noticed.

Credit: security@xen.org

Affected SoftwareAffected VersionHow to fix
debian/xen<=4.11.4+107-gef32c7afa2-1
4.14.6-1
4.14.5+94-ge49571868d-1
4.17.1+2-gb773c48e36-1
4.17.2+55-g0b56bed864-1
Xen xen-unstable>=4.0.0
Debian=11.0
Fedora=33
Fedora=34
Fedora=35

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Reference Links

Frequently Asked Questions

  • What is the severity of CVE-2021-28701?

    CVE-2021-28701 has a medium severity level that can lead to unauthorized access to Xen-owned memory pages.

  • How do I fix CVE-2021-28701?

    To fix CVE-2021-28701, update to the latest version of Xen that is unaffected by this vulnerability.

  • What versions of Xen are affected by CVE-2021-28701?

    CVE-2021-28701 affects Xen versions starting from 4.0.0 up to 4.11.4+107-gef32c7afa2-1.

  • Who is affected by CVE-2021-28701?

    Users running affected versions of Xen, especially in Debian and Fedora environments, are at risk with CVE-2021-28701.

  • What impact does CVE-2021-28701 have on guest users?

    CVE-2021-28701 allows guest users to access certain Xen-controlled memory pages, potentially compromising the security of the host system.

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