{"id":"CVE-2021-28701","details":"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.","modified":"2026-03-15T22:37:00.676272Z","published":"2021-09-08T14:15:08.547Z","related":["SUSE-SU-2021:14848-1","SUSE-SU-2021:3140-1","SUSE-SU-2021:3140-2","SUSE-SU-2021:3141-1","SUSE-SU-2021:3181-1","SUSE-SU-2021:3213-1","SUSE-SU-2021:3322-1","SUSE-SU-2021:3842-1","SUSE-SU-2021:3849-1","SUSE-SU-2021:3977-1","openSUSE-SU-2021:1301-1","openSUSE-SU-2021:3140-1"],"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3HEHUIUWSSMCQGQY3GWX4J2SZGYP5W2Z/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CEHZLIR5DFYYQBH55AERWHLO54OFU42C/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L4MI3MQAPGILCLXBGQWPZHGE3ALSO4ZU/"},{"type":"ADVISORY","url":"http://xenbits.xen.org/xsa/advisory-384.html"},{"type":"ADVISORY","url":"https://security.gentoo.org/glsa/202208-23"},{"type":"ADVISORY","url":"https://www.debian.org/security/2021/dsa-4977"},{"type":"ADVISORY","url":"https://xenbits.xenproject.org/xsa/advisory-384.txt"},{"type":"ADVISORY","url":"http://www.openwall.com/lists/oss-security/2021/09/08/2"}],"affected":[{"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-28701.json","unresolved_ranges":[{"events":[{"introduced":"4.0.0"}]},{"events":[{"introduced":"0"},{"last_affected":"11.0"}]},{"events":[{"introduced":"0"},{"last_affected":"33"}]},{"events":[{"introduced":"0"},{"last_affected":"34"}]},{"events":[{"introduced":"0"},{"last_affected":"35"}]}]}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H"}]}