CVE-2026-3842: Qemu-kvm: hyperv/syndbg: missing mapped-length guard after cpu_physical_memory_map causes host oob write

highCVSS 7.8CVE-2026-3842

CSIRTS triage

vendor: QEMU product: QEMU Privilege escalation

What: A missing mapped-length guard after cpu_physical_memory_map can cause an out-of-bounds write on the host.
Who is affected: Deployments of QEMU with hyperv/syndbg enabled.
Urgency: High urgency due to the potential for privilege escalation.
Action: Apply the latest security updates for QEMU.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.8
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-3842

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-38420.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-3842	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Qemu-kvm

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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