# CVE-2026-89571: cxl/features: bound fwctl command payload to the input buffer

> A missing bounds check in the Linux kernel CXL feature driver allows out-of-bounds reads, potentially causing a kernel crash or leaking memory.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89571, DEBIAN-CVE-2026-89571, GHSA-x7fx-9652-j55v, UBUNTU-CVE-2026-89571

## What is CVE-2026-89571?

CVE-2026-89571 is a high-severity memory corruption vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

cxl/features: bound fwctl command payload to the input buffer

fwctl_cmd_rpc() copies cmd->in_len bytes into inbuf = kvzalloc(cmd->in_len)
and passes inbuf and in_len to ->fw_rpc(). The CXL callback cxlctl_fw_rpc()
ignores in_len and never checks the user-controlled op_size against it.

cxlctl_set_feature() bounds op_size only from below
(op_size <= sizeof(feat_in->hdr)) and then reads op_size - sizeof(hdr)
bytes from feat_in->feat_data via cxl_set_feature(). With a small in_len
and a large op_size the first memcpy() already reads past the
kvzalloc(in_len) buffer; the out-of-bounds bytes are placed in the mailbox
payload and sent to the device, and a large enough op_size can walk into
unmapped memory and oops the kernel. The Get paths pin op_size to a fixed
size but likewise read the input struct without checking in_len.

Reject, at the single dispatch point, any request whose fixed header plus
op_size does not fit in the copied-in buffer. The lower-bound test guards
the subtraction and ensures op_size was copied in before it is read.

## Which versions are affected by CVE-2026-89571?


## How do I fix CVE-2026-89571?

Apply the vendor's patch.

## Is CVE-2026-89571 being exploited?

There is no known exploitation of CVE-2026-89571 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89571 and fix it if it is affected.

What it is: CVE-2026-89571 is a high-severity memory corruption vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89571 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-2026-89571/ (Markdown: https://insights.sbomify.com/CVE-2026-89571/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89571
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89571
- OSV: https://osv.dev/vulnerability/CVE-2026-89571

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89571/
Summaries are generated and may contain mistakes; the official description above is the record.