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Fencer Vulns
medium 4.3

CVE-2026-79603 json

Unconditionally do TLB flushing ahead of page scrubbing

published 2026-09-08 2 mo ago modified 2026-09-08 2 mo ago also EUVD-2026-72721

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 12%
public exploits
0
none known

Summary

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

Patch / fix

  • xen Debian 12 4.17.7+13-g2445b30a44-0+deb12u1
  • xen Debian 13 4.20.4+39-gf1e1321c87-0+deb13u1
  • xen Debian 14 4.20.4+39-gf1e1321c87-1

debian advisories DEBIAN-CVE-2026-79603

  • xen SLE Module for Server Applications 15 SP7, SLE Module for Basesystem 15 SP7 4.20.4_04-150700.3.46.1
  • xen SLE Micro 5.4, SLE Micro 5.3 4.16.7_14-150400.4.92.1
  • xen SLE Micro 5.5 4.17.6_16-150500.3.79.1

suse advisories SUSE-SU-2026:4090-1SUSE-SU-2026:4088-1SUSE-SU-2026:4087-1

  • xen openSUSE Tumbleweed 4.22.0_04-1.1

opensuse advisories openSUSE-SU-2026:11738-1

  • xen Alpine 3.21 4.19.6-r1
  • xen Alpine 3.23, Alpine 3.22 4.20.4-r1
  • xen Alpine 3.24 4.21.2-r1

alpine advisories ALPINE-CVE-2026-79603

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-79603 updated cvss 8.4

xen: Xen: PV guests can modify scrubbed memory pages due to stale TLB entries

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.22% chance of exploitation in the next 30 days, higher than 12% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected products

  • Xen Xen

Classification

Weakness
  • CWE-664 Improper Control of a Resource Through its Lifetime

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.