CVE-2026-80789

What the bug is

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.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/nvme/target/tcp.c

What this is

NVM EXPRESS TARGET DRIVERMAINTAINERS section matched on drivers/nvme/target/ · linux-nvme@lists.infradead.org · Supported

Kernel module

nvmet_tcp

Check it on the machine

grep -w CONFIG_NVME_TARGET_TCP /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

lsmod | grep -w nvmet_tcp

Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.

Show whether Debian builds this, per release

Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.

• bookworm, trixie, forky, sid, bookworm · linux-6.12m

m

a loadable module on every flavour - check lsmod, can be blacklisted

Build switch

CONFIG_NVME_TARGET_TCP

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-09-04 (44 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.23%, higher than 13.3% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/nvme

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
5.0	5.10.269	f6e51b09cbaa
5.0	5.15.220	f63e89a03102
5.0	6.1.187	0952541b153e
5.0	6.6.156	25ad03d5c0e8
5.0	6.12.106	d2acc96c528d
5.0	6.18.47	6d27199ebe8c
5.0	7.1.11	14dbe37681a6
5.0	7.2.1	d895e66628f9
5.0	7.3	4a3f00262a04

Debian advisories