GHSA-46H3-R5W2-2VQQ
Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-16 15:31In 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.
{
"affected": [],
"aliases": [
"CVE-2026-89968"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-16T11:17:07Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnvmet-tcp: reject unsolicited H2CData PDUs\n\nnvmet_tcp_handle_h2c_data_pdu() accepts an H2CData PDU after only checking\nthat its TTAG is a valid in-range command index and that the command\u0027s\ndata buffers are mapped. It never checks that the target has actually\nsolicited that data by sending an R2T for the command.\n\nA remote host can abuse this. It submits a write command that takes the\nR2T path and, before the target transmits the R2T, sends an H2CData PDU\nfor that command\u0027s tag. The data completes the command early, and when\nthe command then fails synchronously (e.g. a length mismatch caught by\nnvmet_check_transfer_len()), it is completed a second time. Each\ncompletion calls nvmet_tcp_queue_response(), so the same command is added\nto queue-\u003eresp_list twice while it is still linked; the second llist_add()\nmakes the node point to itself (lentry-\u003enext == lentry).\n\nnvmet_tcp_process_resp_list() then walks that self-referential node and\nadds the command to resp_send_list twice. With CONFIG_DEBUG_LIST this\ntrips the \"list_add double add\" check (kernel BUG); without it the loop\nnever terminates and the nvmet_tcp workqueue wedges (soft-lockup). It is\nremotely triggerable and needs no authentication on an allow_any_host\nsubsystem.\n\nTrack whether an R2T has been transmitted for a command and reject an\nH2CData PDU that arrives before it. The flag is cleared on command reuse\n(nvmet_tcp_get_cmd() zeroes cmd-\u003eflags) and stays set across the multiple\nH2CData PDUs of a single solicited transfer.",
"id": "GHSA-46h3-r5w2-2vqq",
"modified": "2026-09-16T15:31:03Z",
"published": "2026-09-16T12:30:43Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89968"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/02341ee424fb2eed16b5b8a9d247492e49335c21"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/14beef7d4f123fb458fc9844aa74a071871dcca6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1cbed7538946c99e585acefd11c9ba3a0bdbae05"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2b71f9193e3d3a352920ba367f1a6db345249038"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9fb527103e53fd43a8e802c2eca407869c204f7a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cade124c06f8e738e3a0df285ed2e08953e6bfaa"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cf1484d9a75de6809ef331e16f525aaa41b0e16d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/db62b35cbca052860c519cbcabe7650708528738"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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