CVE-2021-28695: Xen xen vulnerability

CVE-2021-28695: IOMMU page mapping issues on x86 T[his CNA information record relates to multiple CVEs; the text explains w...

IOMMU page mapping issues on x86 T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Both AMD and Intel allow ACPI tables to specify regions of memory which should be left untranslated, which typically means these addresses should pass the translation phase unaltered. While these are typically device specific ACPI properties, they can also be specified to apply to a range of devices, or even all devices. On all systems with such regions Xen failed to prevent guests from undoing/replacing such mappings (CVE-2021-28694). On AMD systems, where a discontinuous range is specified by firmware, the supposedly-excluded middle range will also be identity-mapped (CVE-2021-28695). Further, on AMD systems, upon de-assigment of a physical device from a guest, the identity mappings would be left in place, allowing a guest continued access to ranges of memory which it shouldn't have access to anymore (CVE-2021-28696).

UnknownCVSS not scoredNot KEV-listedUpdatedAug 3, 2024, 21:47 UTC (UTC+00:00)

Security readout for executives and security teams

This is a Xen hypervisor isolation flaw affecting certain AMD x86 hosts. Firmware can describe memory ranges that should bypass IOMMU translation, but Xen could identity-map an excluded middle range when that firmware range was discontinuous. A guest may gain access to memory ranges it should not reach. Exposure is most likely on AMD x86 Xen hosts running affected Xen versions where firmware ACPI tables define discontinuous untranslated IOMMU regions. Risk is especially relevant to environments relying on guest isolation around device and memory mappings. The sources do not prove every AMD Xen host is affected. Treat this as a high-priority virtualization platform issue if the organization runs Xen on AMD x86 hosts. It can affect guest isolation, which is a core control in multi-tenant or sensitive workloads. Prioritize patch verification over emergency response unless other intelligence shows exploitation. Mitigation focus: Apply Xen or distribution security updates referenced by Xen, Debian, Fedora, or Gentoo advisories.; Prioritize AMD x86 Xen hosts running affected 4.11.x through 4.15.x branches.; Review Xen XSA-378 for exact fixed package versions and operational guidance..

Prepared: Jun 2, 2026, 18:39 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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CVE-2021-28695 mapping review

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Vulnerability profileCVE Program record

Severity: Unknown
CVSS: Not scored
Known Exploited: No
Published: Aug 27, 2021, 18:46 UTC (UTC+00:00)

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors

0Timeline events

0ADP providers

7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

CVE List V5 sourceCVE List V5
https://xenbits.xenproject.org/xsa/advisory-378.txtCVE reference · x_refsource_MISC
FEDORA-2021-4f129cc0c1CVE reference · vendor-advisory, x_refsource_FEDORA
FEDORA-2021-d68ed12e46CVE reference · vendor-advisory, x_refsource_FEDORA
DSA-4977CVE reference · vendor-advisory, x_refsource_DEBIAN
FEDORA-2021-081f9bf5d2CVE reference · vendor-advisory, x_refsource_FEDORA
GLSA-202208-23CVE reference · vendor-advisory, x_refsource_GENTOO

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus

Xenxen4.11.xListed

Xenxenxen-unstableListed

Xenxen4.12.xListed

Xenxen4.14.xListed

Xenxen4.15.xListed

Xenxen4.13.xListed

Weakness

CWE details

No CWE listed

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