Bug 2550647 (CVE-2026-79609) - CVE-2026-79609 xen: Xen: Denial of Service via guest page table access beyond direct memory mapping
Summary: CVE-2026-79609 xen: Xen: Denial of Service via guest page table access beyond...
Keywords:
Status: NEW
Alias: CVE-2026-79609
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On: 2559183
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-10-13 15:51 UTC by OSIDB Bzimport
Modified: 2026-10-22 17:29 UTC (History)
0 users

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Description OSIDB Bzimport 2026-10-13 15:51:53 UTC 
XPTI (Xen Page Table Isolation) was introduced to mitigate Meltdown
(CVE-2017-5754, one aspect of XSA-254).  This involves copying 64-bit PV
guest page table entries from guest-chosen root page tables to the Xen-
chosen one which is in actual use by hardware.  To read the guest root
page table, the directmap is used.  PV guests, however, have a directmap
which may not cover all memory; in particular this is the case if any
memory extends beyond the 5 TiB (CONFIG_BIGMEM=y: 3.5 TiB) address
boundary.
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