# CVE-2026-43406: libceph: prevent potential out-of-bounds reads in process_message_header()

> A maliciously corrupted message frame can cause out-of-bounds reads in the Linux kernel's Ceph client, potentially leading to crashes or data exposure.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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:** 8 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43406, DEBIAN-CVE-2026-43406, GHSA-pfqf-x57j-qhgm, ROOT-OS-DEBIAN-11-CVE-2026-43406, ROOT-OS-UBUNTU-2204-CVE-2026-43406, ROOT-OS-UBUNTU-2404-CVE-2026-43406, UBUNTU-CVE-2026-43406

## What is CVE-2026-43406?

CVE-2026-43406 is a critical memory corruption vulnerability in Linux kernel, published on 8 May 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:

libceph: prevent potential out-of-bounds reads in process_message_header()

If the message frame is (maliciously) corrupted in a way that the
length of the control segment ends up being less than the size of the
message header or a different frame is made to look like a message
frame, out-of-bounds reads may ensue in process_message_header().

Perform an explicit bounds check before decoding the message header.

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

## Which versions are affected by CVE-2026-43406?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43406?

Apply the vendor's patch.

## Is CVE-2026-43406 being exploited?

There is no known exploitation of CVE-2026-43406 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-2026-43406 and fix it if it is affected.

What it is: CVE-2026-43406 is a critical memory corruption vulnerability in Linux kernel, published on 8 May 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-2026-43406 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-2026-43406/ (Markdown: https://insights.sbomify.com/CVE-2026-43406/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43406
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43406
- OSV: https://osv.dev/vulnerability/CVE-2026-43406

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43406/
Summaries are generated and may contain mistakes; the official description above is the record.