# CVE-2026-89731: cxl/ras: Fix cxl_rch_get_aer_info() out-of-bounds AER register read

> An out-of-bounds read in the Linux kernel CXL RAS driver allows attackers to leak memory or crash the system via crafted AER register reads.

- **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-2026-89731, DEBIAN-CVE-2026-89731, GHSA-qhph-j75q-5546, UBUNTU-CVE-2026-89731

## What is CVE-2026-89731?

CVE-2026-89731 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/ras: Fix cxl_rch_get_aer_info() out-of-bounds AER register read

cxl_rch_get_aer_info() copies the RCH Downstream Port AER capability from
the RCRB MMIO block using a readl() loop bounded by sizeof(struct
aer_capability_regs). This struct is a software layout and its embedded
struct pcie_tlp_log is larger than the on-wire AER capability. As a
result the loop reads past the mapped AER register block.

The over-read also populates the software-only tail fields including
header_log.header_len. An out-of-range header_len passed to
pcie_print_tlp_log() can then loop past the header log buffer and cause
a second out-of-bounds read.

The read was correct when introduced, but struct pcie_tlp_log has since
grown (Header Log and TLP Prefix Log sizes, header_len and flit fields),
so sizeof(struct aer_capability_regs) no longer matches the physical AER
capability.

Bound the read to the physical AER registers, header through the 16 byte
Header Log. Zero the destination first so the software-only fields are
deterministic.

## Which versions are affected by CVE-2026-89731?


## How do I fix CVE-2026-89731?

Apply the vendor's patch.

## Is CVE-2026-89731 being exploited?

There is no known exploitation of CVE-2026-89731 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89731 and fix it if it is affected.

What it is: CVE-2026-89731 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-2026-89731 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-2026-89731/ (Markdown: https://insights.sbomify.com/CVE-2026-89731/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89731
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89731
- OSV: https://osv.dev/vulnerability/CVE-2026-89731

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89731/
Summaries are generated and may contain mistakes; the official description above is the record.