Live › vulnerability › CVE-2026-99123
Go to dashboardA connected AF_VSOCK socket in the Linux kernel can be moved to an established state by a packet from an unrelated source, because the virtio receive path falls back to destination-only socket lookup without checking the source. A local unprivileged process can then inject data into the victim socket, which reads attacker-chosen bytes.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-28 11:32 UTC. All times on this page are UTC.
Systems running a Linux kernel with virtio vsock support, such as virtual machines and hypervisor hosts that use AF_VSOCK for host-guest communication. Exposure depends on local unprivileged users being able to create AF_VSOCK sockets on the machine. Hosts without virtio vsock loaded are unlikely to be affected; the sources do not say more.
No product ranges from the sources yet.
uname -r and compare against the fixed kernel version listed by your distribution's advisory for CVE-2026-99123lsmod | grep -E 'vmw_vsock_virtio_transport|vhost_vsock' to see whether virtio vsock is loaded at allvirtio_vsock and vhost_vsock until patched (unknown whether this fully mitigates on every configuration)Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
In the Linux kernel, the following vulnerability has been resolved:
vsock/virtio: validate packet source for connected sockets
virtio_transport_recv_pkt() looks up sockets first by the full source and destination tuple, then by destination only in the bound table. The fallback is needed for listening and connecting sockets, but sockets remain in the bound table after connect(), so it can also return a non-listening socket.
The fallback does not validate the source address. In TCP_SYN_SENT, a RESPONSE from an unrelated source can transition the victim socket to TCP_ESTABLISHED while its stored remote address remains unchanged. Subsequent RW packets from that source are delivered through the same destination-only fallback.
This was reproduced with capability-empty processes under different UIDs. The attacker discovered the target tuple through unprivileged AF_VSOCK sock_diag and caused the victim socket to read 16 attacker-chosen bytes; the intended peer-side socket read 0 of those 16 bytes.
Add vsock_check_source() to validate the transport, source port and source CID against the peer stored in a non-listening socket. The local transport is the CID exception because its packets are generated internally with VMADDR_CID_LOCAL as their source, including connections using CID aliases.
Use the helper after lock_sock() in the virtio receive path.
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