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QEMU CVE-2026-3842

| EUVDEUVD-2026-44840 HIGH
Out-of-bounds Write (CWE-787)
2026-07-16 fedora GHSA-6mwr-p34x-55cv
Authentication Bypass Buffer Overflow Denial Of Service Information Disclosure Memory Corruption Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 6 Red Hat Enterprise Linux 7 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Red Hat Openshift Container Platform 4 Red Hat
7.8
CVSS 3.1 · Vendor: fedora
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Severity by source

Vendor (fedora) PRIMARY
7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
7.8 HIGH

Attacker needs guest code execution (AV:L, PR:L) via a low-complexity emulation path with no user interaction, yielding high C/I/A from host-process heap corruption; scope kept U per the description's focus on QEMU/guest memory.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Ubuntu
MEDIUM
qualitative
SUSE
5.1 MEDIUM
AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Red Hat
7.8 HIGH
qualitative

Primary rating from Vendor (fedora).

CVSS VectorVendor: fedora

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Analysis Generated
Jul 16, 2026 - 01:13 vuln.today
CVE Published
Jul 16, 2026 - 00:20 cve.org
HIGH 7.8

DescriptionCVE.org

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.

AnalysisAI

Out-of-bounds heap write in QEMU lets a local attacker operating inside a guest virtual machine corrupt memory in the host emulator process, enabling information disclosure, data-integrity corruption, or denial of service. The flaw stems from cpu_physical_memory_map() returning a shorter buffer length than the caller assumes, so subsequent writes spill past the allocation. Rated CVSS 7.8 (CWE-787); no public exploit identified at time of analysis, but multiple distributions (Red Hat, Ubuntu, SUSE, Debian) have shipped fixes.

Technical ContextAI

QEMU is the machine emulator/virtualizer underpinning KVM-based virtualization across major Linux distributions and cloud/container platforms. The bug is a classic CWE-787 out-of-bounds write: device/DMA emulation code calls cpu_physical_memory_map() to obtain a host pointer into guest physical memory and writes an expected number of bytes, but the function can legitimately map fewer bytes than requested (for example when a request straddles a memory-region boundary or non-contiguous RAM). When the caller does not honor the shortened returned length, it writes beyond the mapped region into adjacent QEMU heap-allocated objects. Because this executes within the privileged QEMU process on the host, corruption of heap metadata or neighboring objects is the root primitive attackers would pursue.

RemediationAI

Apply the QEMU package updates from your distribution as the primary fix: Ubuntu via USN-8161-1 (https://ubuntu.com/security/notices/USN-8161-1), SUSE via the referenced SUSE-SU-2026 advisories (for example https://www.suse.com/support/update/SUSE-SU-2026:21883/), and Red Hat per its errata linked from https://access.redhat.com/security/cve/CVE-2026-3842 for RHEL 6-10 and OpenShift Container Platform 4. Because the affected code is core emulation, updating the QEMU packages and then restarting or live-migrating running guests is required for the fix to take effect, since a running VM keeps the vulnerable binary mapped until the process is recycled. Exact fixed versions are per-distro and should be cited from the advisories rather than assumed. If patching must be deferred, reduce exposure by limiting untrusted guests on shared hosts, minimizing emulated device surface (disable unneeded emulated devices or DMA/passthrough paths), and isolating multi-tenant workloads onto separate hosts; these controls shrink the attacker population and blast radius but do not remove the underlying flaw.

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Remote code execution in Cockpit's web interface allows unauthenticated attackers to execute arbitrary commands on the h
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Remote code execution in Samba's printing subsystem allows remote attackers to inject arbitrary shell commands via craft
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Authentication bypass in 389 Directory Server (shipped as Red Hat Directory Server 11-13 and within RHEL 6-10) lets remo
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Remote code execution and privilege escalation in HPLIP (HP Linux Imaging and Printing) affects the hpcups print filter

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Unauthenticated privilege escalation in FreeIPA (Red Hat Identity Management) allows a remote attacker to gain genuine a
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7.5 Mar 30

Remote code execution in libarchive on 32-bit systems allows unauthenticated attackers to execute arbitrary code via spe
CVE-2026-28369 CRITICAL
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HTTP request smuggling in Undertow (the embedded web server underpinning JBoss EAP, Red Hat Data Grid, and Apache Camel

CVE-2026-28368 CRITICAL
9.1 Mar 27

HTTP request smuggling in Red Hat Undertow allows remote unauthenticated attackers to bypass front-end security controls
CVE-2026-33845 CRITICAL
9.1 Apr 30

Out-of-bounds read in the GnuTLS DTLS handshake reassembly logic lets remote unauthenticated attackers trigger an intege
CVE-2026-28367 CRITICAL
9.1 Mar 27

HTTP request smuggling in Undertow allows remote unauthenticated attackers to send `\r\r\r` as a header block terminator
CVE-2026-16526 HIGH
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Local privilege escalation in Performance Co-Pilot (PCP) on Red Hat Enterprise Linux 6 through 10 and OpenShift Containe

Same weakness CWE-787 – Out-of-bounds Write

View all
CVE-2015-3113 CRITICAL POC
9.8
CVE-2011-2462 CRITICAL POC
9.8
CVE-2012-1889 HIGH POC
8.8
CVE-2010-3333 HIGH POC
7.8
CVE-2014-1761 HIGH POC
7.8
CVE-2009-3129 HIGH POC
7.8
CVE-2021-1732 HIGH POC
7.8
CVE-2013-3346 CRITICAL POC
9.8

Same technique Authentication Bypass

View all
CVE-2023-22515 CRITICAL POC
9.8
CVE-2012-4681 CRITICAL POC
9.8
CVE-2013-2465 CRITICAL POC
9.8
CVE-2011-3544 CRITICAL POC
9.8
CVE-2022-40684 CRITICAL POC
9.8
CVE-2025-61882 CRITICAL POC
9.8
CVE-2024-0012 CRITICAL POC
9.3
CVE-2023-46805 HIGH POC
8.2

Vendor StatusVendor

Ubuntu

Priority: Medium
qemu
Release Status Version
resolute needed -
trusty needs-triage -
xenial needs-triage -
bionic needs-triage -
focal needs-triage -
upstream needs-triage -
jammy not-affected code not present
noble released 1:8.2.2+ds-0ubuntu1.16
questing released 1:10.1.0+ds-5ubuntu2.6
USN-8161-1

Debian

qemu
Release Status Fixed Version Urgency
bullseye not-affected - -
bullseye (security) fixed 1:5.2+dfsg-11+deb11u5 -
bookworm vulnerable 1:7.2+dfsg-7+deb12u18 -
bookworm (security) vulnerable 1:7.2+dfsg-7+deb12u15 -
trixie fixed 1:10.0.10+ds-0+deb13u1 -
trixie (security) vulnerable 1:10.0.2+ds-2+deb13u1 -
forky, sid fixed 1:11.0.2+ds-2 -
(unstable) fixed 1:10.2.2+ds-1 -

SUSE

Severity: Moderate
Product Status
Container suse/sl-micro/6.0/base-os-container:latest Container suse/sl-micro/6.0/toolbox:latest Image SL-Micro Image SLE-Micro Image SLE-Micro-Azure Image SLE-Micro-BYOS Image SLE-Micro-BYOS-Azure Image SLE-Micro-BYOS-EC2 Image SLE-Micro-BYOS-GCE Image SLE-Micro-EC2 Image SLE-Micro-GCE Affected
Container suse/sl-micro/6.0/kvm-os-container:2.1.3-6.161 Container suse/sl-micro/6.1/kvm-os-container:2.2.0-3.3 Affected
Container suse/sle-micro/kvm-5.5:2.0.4-3.5.543 Affected
Image SLES15-SP6-EC2-ECS-HVM Affected
Image SLES15-SP7-EC2-ECS-HVM Affected

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CVE-2026-3842 vulnerability details – vuln.today
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