CVE-2026-3842 Qemu-kvm: hyperv/syndbg: missing mapped-length guard after cpu_physical_memory_map causes host oob write
A local attacker in a guest VM can trigger an out-of-bounds write in QEMU, leading to memory corruption, information disclosure, or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-3842?
CVE-2026-3842 is a high-severity memory corruption vulnerability in Red Hat Enterprise Linux 10, published on 16 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
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.
Weakness: CWE-787
Which versions are affected by CVE-2026-3842?
How do I fix CVE-2026-3842?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-3842 being exploited?
There is no known exploitation of CVE-2026-3842 in the wild and no public exploit code.
Sources
Also known as AZL-92502, BELL-CVE-2026-3842, DEBIAN-CVE-2026-3842, ECHO-334b-1c04-aa69, GHSA-6mwr-p34x-55cv, UBUNTU-CVE-2026-3842.