# CVE-2026-90067: libceph: validate banner payload length

> A remote attacker can trigger a kernel warning and potential denial of service by sending a Ceph messenger v2 banner with an invalid payload length.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-102594, BELL-CVE-2026-90067, DEBIAN-CVE-2026-90067, GHSA-prv5-g54g-rmhh, UBUNTU-CVE-2026-90067

## What is CVE-2026-90067?

CVE-2026-90067 is a high-severity denial of service vulnerability in Linux, published on 17 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:

libceph: validate banner payload length

When parsing the Ceph messenger v2 protocol banner, the `payload_len` field
is decoded from the banner prefix. If a client sends a banner with a
`payload_len` of 0, the kernel sets up a 0-length socket read. This
violates an invariant in the state machine, triggering a warning in
`populate_in_iter()`:

------------[ cut here ]------------
!iov_iter_count(&con->v2.in_iter)
WARNING: net/ceph/messenger_v2.c:3129 at populate_in_iter
net/ceph/messenger_v2.c:3129 [inline], CPU#1: kworker/1:3/5070
WARNING: net/ceph/messenger_v2.c:3129 at ceph_con_v2_try_read+0x6634/0x6810
net/ceph/messenger_v2.c:3159, CPU#1: kworker/1:3/5070
...
Call Trace:
 <TASK>
 ceph_con_workfn+0x1f5/0x14a0 net/ceph/messenger.c:1575
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

According to the msgr2 protocol specification, the banner payload is
expected to contain at least two 64-bit integers (`server_feat` and
`server_req_feat`). Therefore, `payload_len` must be at least 16 bytes.

Fix this by adding a check in `process_banner_prefix()` to reject a
`payload_len` smaller than 16 bytes. This prevents the 0-length read and
correctly aborts the connection with a protocol error.

## Which versions are affected by CVE-2026-90067?


## How do I fix CVE-2026-90067?

Apply the vendor's patch.

## Is CVE-2026-90067 being exploited?

There is no known exploitation of CVE-2026-90067 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90067 and fix it if it is affected.

What it is: CVE-2026-90067 is a high-severity denial of service vulnerability in Linux, published on 17 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-2026-90067 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-2026-90067/ (Markdown: https://insights.sbomify.com/CVE-2026-90067/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90067
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90067
- OSV: https://osv.dev/vulnerability/CVE-2026-90067

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90067/
Summaries are generated and may contain mistakes; the official description above is the record.