CVE-2021-28701

mediumpriority · track · 31EPSS 0.003 · 18 %ileEURUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.27% (18th) EPSS

CVSS 4.4 · medium

Is it mine?

16 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · fstec_bdu · nvd

EPSS · scored 2026-10-27

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.

cvss

Technical severity, 0–10. One row per scoring source.

7.8

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 4.4–7.8

v2.04.4mediumAV:L/AC:M/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 3.4 · impact 6.4

v3.17.8highCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 1.1 · impact 6

v3.17.8highAV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.17.1highCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-362USprimaryCWE-269US

affected products (16)

Products and version ranges known to be affected.

Xen Xen≤ 4.11.xenisa_euvdEU
Xen Xen4.12.x → unspecifiedenisa_euvdEU
Xen Xen4.15.x → unspecifiedenisa_euvdEU
Fedora Project Fedora≤ 33fstec_bduRU
Fedora Project Fedora≤ 35fstec_bduRU
Fedora Project Fedora≤ 34fstec_bduRU
The Linux Foundation Xen4.0.0 → 4.14.3-1fstec_bduRU
АО «НППКТ» ОСОН ОСнова Оnyx≤ 2.6fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 10fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 9fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 11fstec_bduRU
debian debian linux= 11.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
fedoraproject fedora= 33nvdUScpe:2.3:o:fedoraproject:fedora:*:*:*:*:*:*:*:*
fedoraproject fedora= 34nvdUScpe:2.3:o:fedoraproject:fedora:*:*:*:*:*:*:*:*
fedoraproject fedora= 35nvdUScpe:2.3:o:fedoraproject:fedora:*:*:*:*:*:*:*:*
xen xen≥ 4.0.0nvdUScpe:2.3:o:xen:xen:*:*:*:*:*:*:*:*

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu nvd NVD CVE.org MITRE

published 2021-09-08modified 2026-06-17

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+4135 more

references (36)

External citations — patches, advisories, analysis.

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