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Fencer Vulns
high 7.8

CVE-2026-3842 json

Qemu-kvm: hyperv/syndbg: missing mapped-length guard after cpu_physical_memory_map causes host oob write

published 2026-07-16 3 mo ago modified 2026-09-01 2 mo ago also EUVD-2026-44840

cvss
7.8
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 6%
public exploits
0
none known

Summary

A flaw was found in QEMU. This vulnerability allows a local attacker within a guest virtual machine to write data beyond its allocated memory. This occurs when cpu_physical_memory_map() returns a shorter length than expected, leading to an out-of-bounds write. Successful exploitation could result in unauthorized access to guest memory or corruption of heap-allocated objects, potentially causing information disclosure, data integrity issues, or a denial of service.

Patch / fix

  • qemu Debian 13 1:10.0.10+ds-0+deb13u1
  • qemu Debian 14 1:10.2.2+ds-1

debian advisories DEBIAN-CVE-2026-3842

  • qemu Ubuntu 24.04 LTS 1:8.2.2+ds-0ubuntu1.16
  • qemu Ubuntu 25.10 1:10.1.0+ds-5ubuntu2.6

ubuntu advisories UBUNTU-CVE-2026-3842

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • qemu SLE Module for Server Applications 15 SP7, SLE Micro 5.5 7.1.0-150500.49.42.1
  • qemu SLE Module for Server Applications 15 SP7, SLE Module for Package Hub 15 SP7, SLE Module for Basesystem 15 SP7 9.2.4-150700.3.20.1
  • qemu-linux-user SLE Module for Package Hub 15 SP7 9.2.4-150700.3.20.1
  • qemu SLES for SAP 15 SP6, SLES 15 SP6-LTSS 8.2.10-150600.3.49.1

suse advisories SUSE-SU-2026:2388-1SUSE-SU-2026:2386-1SUSE-SU-2026:2385-1

  • qemu Azure Linux 3.0 9.1.0-11

azure linux advisories AZL-92502

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-3842 updated cvss 7.8

qemu-kvm: hyperv/syndbg: missing mapped-length guard after cpu_physical_memory_map causes host OOB write

  • Red Hat Enterprise Linux 6 qemu-img, qemu-kvm, qemu-kvm-tools, qemu-guest-agent, qemu-guest-agent-win32 Red Hat Enterprise Linux 7 qemu-img, qemu-kvm, libcacard, qemu-img-ma, qemu-kvm-ma, qemu-kvm-tools, +5 more Red Hat Enterprise Linux 8 qemu-img, qemu-kvm, qemu-kvm-core, qemu-kvm-tests, qemu-kvm-common, qemu-guest-agent, +8 more Red Hat Enterprise Linux 9 qemu-img, qemu-kvm, qemu-kvm-core, qemu-kvm-tools, qemu-pr-helper, qemu-kvm-common, +16 more Red Hat Enterprise Linux 10 qemu-kvm Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    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
total
Assessed
3 mo ago

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CISA ADP 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat OpenShift Container Platform 4

Classification

Weakness

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.