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TI-2021-09769 Aliases CVE-2021-28703GHSA-mj29-93c5-p3pr

grant table v2 status pages may remain accessible after de-allocation (take two) Guest…

Priority LOW 31Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA.

Summary

grant table v2 status pages may remain accessible after de-allocation (take two) Guest get 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, get de-allocated when a guest switched (back) from v2 to v1. The freeing of such pages requires that the hypervisor know where in the guest these pages were mapped. The hypervisor tracks only one use within guest space, but racing requests from the guest to insert mappings of these pages may result in any of them to become mapped in multiple locations. Upon switching back from v2 to v1, the guest would then retain access to a page that was freed and perhaps re-used for other purposes. This bug was fortuitously fixed by code cleanup in Xen 4.14, and backported to security-supported Xen branches as a prerequisite of the fix for XSA-378.

Why it matters now

EPSS 0.00328 26th percentileScored 2026-11-07
Fix Fixed Xen (Xen Project): Branch 4.13.4 4.13.4, Branch 4.14.x 4.14.x, Branch 4.15.x 4.15.x

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
Xen ProjectXenBranch 4.13 – 4.13Branch 4.13.4 4.13.4, Branch 4.14.x 4.14.x, Branch 4.15.x 4.15.xPatch availableCNA
  • Xen VendorXen Project Affected Branch 4.13 – 4.13 Fixed in Branch 4.13.4 4.13.4, Branch 4.14.x 4.14.x, Branch 4.15.x 4.15.x Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:o:xen:xen:*:*:*:*:*:*:x86:*before 14.4VulnerableXen
  • cpe:2.3:o:xen:xen:*:*:*:*:*:*:x86:* Versions before 14.4 Vulnerable ·Xen

Remediation

  • Fix · CNA Xen (Xen Project) Fixed in Branch 4.13.4 4.13.4, Branch 4.14.x 4.14.x, Branch 4.15.x 4.15.x

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-28703
  2. 2026-10-03 Alias added: GHSA-mj29-93c5-p3pr

References

Advisory 2

  • TI-2012-00210 The x86-64 kernel system-call functionality in Xen 4.1.2 and earlier, as used in Citrix… CVSS 2.0HIGH 7.2
  • TI-2023-07042 Information disclosure through error messages in AMD Ryzen™ 3000 Series Desktop… CVSS 3.1MEDIUM 5.5
  • TI-2015-04333 The C+ mode offload emulation in the RTL8139 network card device model in QEMU, as used… CVSS 2.0HIGH 9.3
  • TI-2015-06741 The KVM subsystem in the Linux kernel through 4.2.6, and Xen 4.3.x through 4.6.x, allows… CVSS 3.1CRITICAL 10.0
  • TI-2018-06436 A statement in the System Programming Guide of the Intel 64 and IA-32 Architectures… CVSS 3.0HIGH 7.8
  • TI-2024-20522 x86: Incorrect logic for BTC/SRSO mitigations CVSS 3.1HIGH 7.5
See all 489 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences