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CVE-2026-6426: Qemu-kvm: vhost inflight migration vmstate integer type mismatch causes out-of-bounds access

• Severity: medium (CVSS 4.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-10 · updated 2026-09-18
• Weakness: CWE-681

Description

A type mismatch vulnerability was found in QEMU's vhost inflight migration VMState handling. The destination buffer size is stored as a uint64_t but read by the VMS_VBUFFER load path as a signed int32_t. On little-endian hosts, a crafted incoming migration state with bit 31 set causes the value to be interpreted as negative and then implicitly converted to a very large size_t, leading qemu_get_buffer() to copy migration-stream data beyond the bounds of the mmap-backed inflight region. This can result in a crash of the QEMU process or memory corruption. Exploitation requires control of the migration producer or write access to the migration channel, combined with a destination configured to use vhost inflight migration.

Affected products

• Red Hat OpenShift Container Platform 4.18: all versions
• Red Hat Enterprise Linux 10: all versions
• Red Hat Enterprise Linux 6: all versions
• Red Hat Enterprise Linux 7: all versions
• Red Hat Enterprise Linux 8: all versions
• Red Hat Enterprise Linux 9: all versions

References

• https://access.redhat.com/security/cve/CVE-2026-6426
• https://bugzilla.redhat.com/show_bug.cgi?id=2513498

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