CVE-2026-89968

Status: UPDATED  |  Advisory ID: CVE-2026-89968

Key Details

Affected Products, Subsystems & Sectors

What to Know

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-referential node and

adds the command to resp_send_list twice. With CONFIG_DEBUG_LIST this

trips the "list_add double add" check (kernel BUG); without it the loop

never terminates and the nvmet_tcp workqueue wedges (soft-lockup). It is

remotely triggerable and needs no authentication on an allow_any_host

subsystem.

Track whether an R2T has been transmitted for a command and reject an

H2CData PDU that arrives before it. The flag is cleared on command reuse

(nvmet_tcp_get_cmd() zeroes cmd->flags) and stays set across the multiple

H2CData PDUs of a single solicited transfer. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References