CVE-2026-3842Public exploit

Host memory corruption via unchecked short guest mapping

Published Jul 16, 2026 · Updated Jul 16, 2026

Out-of-bounds write in QEMU 7.1.0 and later before 11.0.0 allows guest OS users to corrupt host memory via Hyper-V SynDbg messages. In hw/hyperv/syndbg.c, handle_recv_msg() writes the requested receive length after cpu_physical_memory_map() returns a shorter mapping. A guest must access an x86 VM configured with hv-syndbg and its required VMBus device; exploitation can corrupt a host heap object, disclose data, or crash QEMU.

CVSS severity7.8
High
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in QEMU 7.1.0 and later before 11.0.0 allows guest OS users to corrupt host memory via Hyper-V SynDbg messages. In hw/hyperv/syndbg.c, handle_recv_msg() writes the requested receive length after cpu_physical_memory_map() returns a shorter mapping. A guest must access an x86 VM configured with hv-syndbg and its required VMBus device; exploitation can corrupt a host heap object, disclose data, or crash QEMU.

The record

CVE
CVE-2026-3842
Published
Jul 16, 2026
Updated
Jul 16, 2026
Vendor
QEMU Project
Product
QEMU
Classifications
CWE-787, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=7.1.0 <11.0.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

QEMU Project · QEMUversion=7.1.0 <11.0.0

Published CVSS scores

7.8Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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