# CVE-2026-46064: ibmasm: fix heap over-read in ibmasm_send_i2o_message()

> A local root user can trigger a heap over-read in the ibmasm driver, leaking kernel memory to the service processor.

- **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:** 27 May 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-88634, BELL-CVE-2026-46064, DEBIAN-CVE-2026-46064, GHSA-4p2m-h7j8-hhxj, ROOT-OS-DEBIAN-11-CVE-2026-46064, ROOT-OS-DEBIAN-12-CVE-2026-46064, ROOT-OS-UBUNTU-2204-CVE-2026-46064, ROOT-OS-UBUNTU-2404-CVE-2026-46064, UBUNTU-CVE-2026-46064

## What is CVE-2026-46064?

CVE-2026-46064 is a high-severity vulnerability in Linux kernel, published on 27 May 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:

ibmasm: fix heap over-read in ibmasm_send_i2o_message()

The ibmasm_send_i2o_message() function uses get_dot_command_size() to
compute the byte count for memcpy_toio(), but this value is derived from
user-controlled fields in the dot_command_header (command_size: u8,
data_size: u16) and is never validated against the actual allocation size.
A root user can write a small buffer with inflated header fields, causing
memcpy_toio() to read up to ~65 KB past the end of the allocation into
adjacent kernel heap, which is then forwarded to the service processor
over MMIO.

Silently clamping the copy size is not sufficient: if the header fields
claim a larger size than the buffer, the SP receives a dot command whose
own header is inconsistent with the I2O message length, which can cause
the SP to desynchronize. Reject such commands outright by returning
failure.

Validate command_size before calling get_mfa_inbound() to avoid leaking
an I2O message frame: reading INBOUND_QUEUE_PORT dequeues a hardware
frame from the controller's free pool, and returning without a
corresponding set_mfa_inbound() call would permanently exhaust it.

Additionally, clamp command_size to I2O_COMMAND_SIZE before the
memcpy_toio() so the MMIO write stays within the I2O message frame,
consistent with the clamping already performed by outgoing_message_size()
for the header field.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-46064?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-46064?

Apply the vendor's patch.

## Is CVE-2026-46064 being exploited?

There is no known exploitation of CVE-2026-46064 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46064 and fix it if it is affected.

What it is: CVE-2026-46064 is a high-severity vulnerability in Linux kernel, published on 27 May 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-2026-46064 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-46064/ (Markdown: https://insights.sbomify.com/CVE-2026-46064/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46064
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46064
- OSV: https://osv.dev/vulnerability/CVE-2026-46064

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46064/
Summaries are generated and may contain mistakes; the official description above is the record.