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

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.

Published: 2026-07-15 Last update: 2026-07-16 Assigner: [email protected] Source: [email protected]
NVD Status：Awaiting Analysis，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-3842 is rated Low Risk (31.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.11%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-3842

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-07-16 — 0.11% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-3842

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Weakness enumeration for CVE-2026-3842

GitHub Security Advisory for CVE-2026-3842

GHSA-6mwr-p34x-55cv · Severity: high — A flaw was found in QEMU. This vulnerability allows a local attacker within a guest virtual...

OS Trackers for CVE-2026-3842

vendor priority summary link
debian unimportant CVE-2026-3842 unimportant priority: Debian including 1 source packages (qemu), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2026-3842
redhat high — https://access.redhat.com/security/cve/CVE-2026-3842
suse medium CVE-2026-3842 severity moderate: SUSE including 45 source package names (qemu, qemu-SLOF, …), 317 product×package rows across 15 product lines (SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS, SUSE Linux Enterprise Micro 5.2, … (15 product lines)): Known Not Affected 317. https://www.suse.com/security/cve/CVE-2026-3842/
ubuntu medium CVE-2026-3842 medium priority: Ubuntu including 1 source packages (qemu), 8 status rows across 8 suites (bionic, focal, jammy, noble, questing, trusty, upstream, xenial): needs-triage 5, released 2, not-affected 1. https://ubuntu.com/security/CVE-2026-3842

Affected software / configurations for CVE-2026-3842

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2026-3842

cvelogic Threat Intelligence