---
id: CVE-2026-80789
title: 'nvmet-tcp: bound SGL data length before allocating command buffers'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nvmet-tcp: bound SGL data length before allocating command buffers

  nvmet_tcp_map_data() reads the host-controlled 32-bit sgl->length
  and, for the in-capsule offset des…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    f63e89a0310264264923f84406dea05fe752de62
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    0952541b153e258b99d39cdb03ea6919fdeb41d0
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    25ad03d5c0e858c4b63f1e4b6d461d2af1b30b22
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    d2acc96c528d589f5827cfb90e8e9229dd9d8cb4
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    6d27199ebe8cb223022150f74be13f154a964474
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    14dbe37681a6a7e346fc147bb363ec7cca3180a0
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    d895e66628f939edbb98608f6e033d3d39e6e546
  - >-
    Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 <
    4a3f00262a044e8e15064b1a6860968bf0500bf4
  - Linux 5.0
published: '2026-09-04'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:43:42.439Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80789'
references:
  - url: 'https://git.kernel.org/stable/c/f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5'
  - url: 'https://git.kernel.org/stable/c/f63e89a0310264264923f84406dea05fe752de62'
  - url: 'https://git.kernel.org/stable/c/0952541b153e258b99d39cdb03ea6919fdeb41d0'
  - url: 'https://git.kernel.org/stable/c/25ad03d5c0e858c4b63f1e4b6d461d2af1b30b22'
  - url: 'https://git.kernel.org/stable/c/d2acc96c528d589f5827cfb90e8e9229dd9d8cb4'
  - url: 'https://git.kernel.org/stable/c/6d27199ebe8cb223022150f74be13f154a964474'
  - url: 'https://git.kernel.org/stable/c/14dbe37681a6a7e346fc147bb363ec7cca3180a0'
  - url: 'https://git.kernel.org/stable/c/d895e66628f939edbb98608f6e033d3d39e6e546'
  - url: 'https://git.kernel.org/stable/c/4a3f00262a044e8e15064b1a6860968bf0500bf4'
tags:
  - cve.org
epss: 0.00234
epssPercentile: 0.13287
ingestedAt: '2026-10-19T10:20:54.958Z'
---

## Overview

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

nvmet-tcp: bound SGL data length before allocating command buffers

nvmet_tcp_map_data() reads the host-controlled 32-bit sgl->length
and, for the in-capsule offset descriptor (type 0x01), checks it
against port->inline_data_size before use. Any other SGL descriptor
type -- including the non-inline transport SGL data-block descriptor
(type (NVME_TRANSPORT_SGL_DATA_DESC << 4) | NVME_SGL_FMT_TRANSPORT_A,
the type a real host uses for out-of-capsule writes) skips that check
entirely and falls straight through to:

	cmd->req.sg = sgl_alloc(len, GFP_KERNEL, &cmd->req.sg_cnt);

with len taken directly from the wire, unbounded up to 4 GiB.

nvmet_req_init() only parses the command and never inspects
sgl->length, and nvmet_check_transfer_len() -- the only other place
transfer_len is validated -- runs later, from req->execute(), after
the allocation has already happened. For a write command the target
responds with an R2T and parks the command waiting for the host to
send the data; if the host (or an unauthenticated peer that simply
never follows up) never does, the sgl_alloc() buffer stays resident
for the life of the command. NVMe/TCP has no mandatory authentication
in the default configuration, so any peer able to reach the target
portal and complete a Fabrics connect can drive this with a single
crafted command, repeatable across queues and connections for
amplification. This is unbounded kernel memory allocation
triggered by a remote, effectively unauthenticated peer.

Validate len against the same NVMET_TCP_MAXH2CDATA ceiling this file
already uses to bound per-PDU H2C data, for every SGL descriptor type,
before doing any allocation. This closes the gap for the non-inline
descriptor while leaving the existing, tighter inline_data_size check
in place for the in-capsule case.

Runtime-verified on a v6.19 KASAN stand: with this bound in place, a
crafted write command carrying an oversized non-inline SGL length is
rejected before sgl_alloc() runs, where the same request previously
drove an unbounded ~256 MiB kernel allocation (up to 4 GiB) that
stayed resident pending an R2T the host never satisfies.

## Affected

- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5`
- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < f63e89a0310264264923f84406dea05fe752de62`
- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < 0952541b153e258b99d39cdb03ea6919fdeb41d0`
- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < 25ad03d5c0e858c4b63f1e4b6d461d2af1b30b22`
- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < d2acc96c528d589f5827cfb90e8e9229dd9d8cb4`
- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < 6d27199ebe8cb223022150f74be13f154a964474`
- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < 14dbe37681a6a7e346fc147bb363ec7cca3180a0`
- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < d895e66628f939edbb98608f6e033d3d39e6e546`
- `Linux >= 872d26a391da92ed8f0c0f5cb5fef428067b7f30 < 4a3f00262a044e8e15064b1a6860968bf0500bf4`
- `Linux 5.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.