QEMU OOB Write via cpu_physical_mem Map Length Mismatch
CVE-2026-3842 Published on July 16, 2026
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.
Vulnerability Analysis
CVE-2026-3842 is exploitable with local system access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Timeline
Reported to Red Hat.
Made public.
Weakness Type
What is a Memory Corruption Vulnerability?
The software writes data past the end, or before the beginning, of the intended buffer. Typically, this can result in corruption of data, a crash, or code execution. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent write operation then produces undefined or unexpected results.
CVE-2026-3842 has been classified to as a Memory Corruption vulnerability or weakness.
Products Associated with CVE-2026-3842
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