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.
See more information about CVE-2021-28701 from MITRE CVE dictionary and NIST NVD
NOTE: The following CVSS v3.0 metrics and score provided are preliminary and subject to review.
|Base Score:||7.8||Base Metrics:||AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H|
|Access Vector:||Local network||Attack Complexity:||High|
|Privileges Required:||Low||User Interaction:||None|
|Integrity Impact:||High||Availability Impact:||High|
|Oracle VM version 3 (xen)||OVMSA-2021-0033||2021-10-07|
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