Vulnerability · Published Jul 16, 2026 · Assigned by fedora
CVE-2026-3842Qemu-kvm: hyperv/syndbg: missing mapped-length guard after cpu_physical_memory_map causes host oob write
High 7.8
In plain English
A high-severity out-of-bounds write in qemu. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 6% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | qemu | no fix listed | DEBIAN-CVE-2026-3842 |
| Debian:13 | qemu | 1:10.0.10+ds-0+deb13u1 | DEBIAN-CVE-2026-3842 |
| Debian:14 | qemu | 1:10.2.2+ds-1 | DEBIAN-CVE-2026-3842 |
| Ubuntu:24.04:LTS | qemu | 1:8.2.2+ds-0ubuntu1.16 | UBUNTU-CVE-2026-3842 |
| Ubuntu:25.10 | qemu | 1:10.1.0+ds-5ubuntu2.6 | UBUNTU-CVE-2026-3842 |
| Ubuntu:26.04:LTS | qemu | no fix listed | UBUNTU-CVE-2026-3842 |
| Ubuntu:26.10 | qemu | no fix listed | UBUNTU-CVE-2026-3842 |
| Ubuntu:26.04:LTS | qemu-hwe | no fix listed | UBUNTU-CVE-2026-3842 |
| Ubuntu:26.10 | qemu-hwe | no fix listed | UBUNTU-CVE-2026-3842 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| qemu | 7.1.0 – before 11.0.0 | |
| Red Hat | Red Hat Enterprise Linux 10 | see references |
| Red Hat | Red Hat Enterprise Linux 6 | see references |
| Red Hat | Red Hat Enterprise Linux 7 | see references |
| Red Hat | Red Hat Enterprise Linux 7 | see references |
| Red Hat | Red Hat Enterprise Linux 8 | see references |
| Red Hat | Red Hat Enterprise Linux 9 | see references |
| Red Hat | Red Hat OpenShift Container Platform 4 | see references |
Weakness: CWE-787 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
References
- https://access.redhat.com/security/cve/CVE-2026-3842 vdb-entry, x_refsource_REDHAT
- RHBZ#2458150 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-3842.json x_sadp-csaf-vex