An assertion failure issue was found in the Network Block Device(NBD) Server in all QEMU versions before QEMU 5.0.1. This flaw occurs when an nbd-client sends a spec-compliant request that is near the boundary of maximum permitted request length. A remote nbd-client could use this flaw to crash the qemu-nbd server resulting in a denial of service.
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Qemu | Qemu | * | 5.0.1 (excluding) |
| Advanced Virtualization for RHEL 8.2.1 | RedHat | virt:8.2-8020120200707202843.11e3e113 | * |
| Advanced Virtualization for RHEL 8.2.1 | RedHat | virt-devel:8.2-8020120200707202843.11e3e113 | * |
| Qemu | Ubuntu | eoan | * |
| Qemu | Ubuntu | focal | * |
| Qemu | Ubuntu | trusty | * |
While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.