# CVE-2026-93228: svcrdma: Reject Write/Reply chunks with segcount 0

> A remote peer can cause a denial of service in the Linux kernel by sending malformed RDMA chunks with zero segments, bypassing validation checks.

- **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:** 24 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-103850, BELL-CVE-2026-93228, DEBIAN-CVE-2026-93228, GHSA-g29j-c673-5ccw, UBUNTU-CVE-2026-93228

## What is CVE-2026-93228?

CVE-2026-93228 is a critical denial of service vulnerability in Linux, published on 24 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:

svcrdma: Reject Write/Reply chunks with segcount 0

A peer can send a Write or Reply chunk whose segcount field is zero.
xdr_check_write_chunk() only rejects segcount > rc_maxpages, so zero
passes the range check, and xdr_inline_decode(stream, 0) returns the
current (non-NULL) cursor without advancing. The function returns
true and pcl_alloc_write() then links a struct svc_rdma_chunk with
ch_segcount == 0 onto rc_write_pcl or rc_reply_pcl.

An earlier patch in this series made pcl_for_each_segment() safe for
ch_segcount == 0, so this no longer drives the memory walk it used
to. Rejecting the malformed frame at the decode boundary is still
worthwhile as defense in depth: it keeps degenerate zero-segment
chunks off the parsed chunk lists entirely, so any future consumer
that walks ch_segments directly cannot observe one, and it makes the
zero-floor easy to backport to trees where the macro change is more
intrusive. RFC 8166 has no meaning for a Write/Reply chunk that
describes no remote buffer, so no legitimate client is affected.

xdr_check_reply_chunk() funnels Reply chunks through
xdr_check_write_chunk() and inherits the same rejection.

pcl_alloc_write() also links each chunk onto the parsed chunk list
before filling its segment array. If a future change weakens the
segcount-0 rejection, an incomplete chunk is visible to consumers
during the fill loop. Reorder so that list_add_tail() follows the
segment fill loop, ensuring only fully-populated chunks appear on
the list.

## Which versions are affected by CVE-2026-93228?


## How do I fix CVE-2026-93228?

Apply the vendor's patch.

## Is CVE-2026-93228 being exploited?

There is no known exploitation of CVE-2026-93228 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93228 and fix it if it is affected.

What it is: CVE-2026-93228 is a critical denial of service vulnerability in Linux, published on 24 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-2026-93228 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-2026-93228/ (Markdown: https://insights.sbomify.com/CVE-2026-93228/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93228
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93228
- OSV: https://osv.dev/vulnerability/CVE-2026-93228

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93228/
Summaries are generated and may contain mistakes; the official description above is the record.