CVE-2026-89968

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

nvmet-tcp: reject unsolicited H2CData PDUs

nvmet_tcp_handle_h2c_data_pdu() accepts an H2CData PDU after only checking

that its TTAG is a valid in-range command index and that the command's

data buffers are mapped. It never checks that the target has actually

solicited that data by sending an R2T for the command.

A remote host can abuse this. It submits a write command that takes the

R2T path and, before the target transmits the R2T, sends an H2CData PDU

for that command's tag. The data completes the command early, and when

the command then fails synchronously (e.g. a length mismatch caught by

nvmet_check_transfer_len()), it is completed a second time. Each

completion calls nvmet_tcp_queue_response(), so the same command is added

to queue->resp_list twice while it is still linked; the second llist_add()

makes the node point to itself (lentry->next == lentry).

nvmet_tcp_process_resp_list() then walks that self-refere

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References