# CVE-2026-89482: nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone

> A flaw in the Linux kernel NVMe-TCP driver allows memory corruption via wild-memory-access, potentially leading to code execution or system crashes.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100148, BELL-CVE-2026-89482, DEBIAN-CVE-2026-89482, GHSA-m28h-7j27-xfqp, UBUNTU-CVE-2026-89482

## What is CVE-2026-89482?

CVE-2026-89482 is a critical memory corruption vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone

Commit 25e5cb780e62 ("nvme-tcp: fix possible crash in write_zeroes
processing") established that blk_rq_payload_bytes() must not be read
without first checking blk_rq_nr_phys_segments(), and recorded the
result in nvme_tcp_setup_cmd_pdu() as req->data_len. The receive side
was left as it was.

The two differ for REQ_OP_WRITE_ZEROES, which has no physical segments
but a non-zero blk_rq_bytes(), so setup leaves req->iter untouched
while the receive gate lets a C2HData through and nvme_tcp_recv_data()
copies into whatever the previous command on that tag left there. The
driver-private area is zeroed only when the tag set is allocated.

Reproduced with a test target that leaves a residual iterator on a tag
and then sends a C2HData for a WRITE_ZEROES command on the same tag:

BUG: KASAN: wild-memory-access in _copy_to_iter+0x642/0x1330
Write of size 512 at addr ffe728c2175dfa81 by task kworker/0:1H/103

CPU: 0 UID: 0 PID: 103 Comm: kworker/0:1H Not tainted 7.2.0-rc5-NVMETCP-gf5098b6bae76 #1 PREEMPT(lazy)
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: nvme_tcp_wq nvme_tcp_io_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x53/0x70
 kasan_report+0xce/0x100
 ? _copy_to_iter+0x642/0x1330
 kasan_check_range+0x105/0x1b0
 __asan_memcpy+0x3c/0x60
 _copy_to_iter+0x642/0x1330
 ? __pfx_sock_has_perm+0x10/0x10
 ? worker_thread+0x45b/0xd10
 ? __pfx__copy_to_iter+0x10/0x10
 ? _raw_spin_lock_bh+0x83/0xe0
 ? __pfx__raw_spin_lock_bh+0x10/0x10
 __skb_datagram_iter+0xf3/0x820
 ? __pfx_simple_copy_to_iter+0x10/0x10
 ? __asan_memcpy+0x3c/0x60
 ? skb_copy_bits+0x58d/0x830
 skb_copy_datagram_iter+0x37/0x120
 nvme_tcp_recv_skb+0xa07/0x4320
 ? __pfx_nvme_tcp_recv_skb+0x10/0x10
 __tcp_read_sock+0x1ab/0x810
 ? __pfx_nvme_tcp_recv_skb+0x10/0x10
 ? __pfx_lock_sock_nested+0x10/0x10
 ? __pfx___tcp_read_sock+0x10/0x10
 nvme_tcp_try_recv+0x152/0x1e0
 ? __pfx_nvme_tcp_try_recv+0x10/0x10
 ? __pfx_mutex_unlock+0x10/0x10
 nvme_tcp_io_work+0x1e4/0x6c0
 ? __schedule+0x181a/0x49f0
 ? __pfx_nvme_tcp_io_work+0x10/0x10
 process_one_work+0x633/0x1030

Keep the blk_rq_payload_bytes() test and add req->data_len to it. The
old test is what rejects a C2HData naming a tag that is no longer in
flight, because blk_update_request() zeroes rq->__data_len on
completion; req->data_len and req->curr_bio are driver-private and
survive completion, so they cannot stand in for it. Setup initialises
the iterator only when both req->curr_bio and req->data_len are set, so
the gate now tests the same two.

## Which versions are affected by CVE-2026-89482?


## How do I fix CVE-2026-89482?

Apply the vendor's patch.

## Is CVE-2026-89482 being exploited?

There is no known exploitation of CVE-2026-89482 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89482 and fix it if it is affected.

What it is: CVE-2026-89482 is a critical memory corruption vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89482 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-89482/ (Markdown: https://insights.sbomify.com/CVE-2026-89482/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89482
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89482
- OSV: https://osv.dev/vulnerability/CVE-2026-89482

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89482/
Summaries are generated and may contain mistakes; the official description above is the record.