# CVE-2026-93264: RDMA/efa: Fix PBL chunk length computation

> A logic error in the EFA RDMA driver causes incorrect chunk length calculations, leading to memory registration failures and potential denial of service.

- **Severity:** Not scored
- **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:** 24 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-93264, DEBIAN-CVE-2026-93264, GHSA-w4pg-rf77-8rgx, UBUNTU-CVE-2026-93264

## What is CVE-2026-93264?

CVE-2026-93264 is a vulnerability in Linux, published on 24 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:

RDMA/efa: Fix PBL chunk length computation

On register MR, when creating the PBL, if it's an indirect PBL we create
a chunk list to hold the PBL pages pointers. Each chunk is 4KB in size
and can hold 510 addresses (EFA_PTRS_PER_CHUNK) and has a 12-byte
control buffer at the end of it holding the next chunk's pointer and its
length.

If the PBL number of pages is a multiple of EFA_PTRS_PER_CHUNK, the
calculated last chunk length is wrongly computed as 0, even though that
chunk is fully populated with 510 real page pointers. This wrong length
is used both to DMA map the chunk and is propagated to the device,
causing the device to see the chunk as empty and reject the memory
registration.

Fix the calculation so it will be performed only if the number of pages
isn't a multiple of EFA_PTRS_PER_CHUNK, if it is, its already handled in
the above loop correctly.
Also prevent out-of-bounds reach in the chunks array in such scenario.

## Which versions are affected by CVE-2026-93264?


## How do I fix CVE-2026-93264?

Apply the vendor's patch.

## Is CVE-2026-93264 being exploited?

There is no known exploitation of CVE-2026-93264 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93264 and fix it if it is affected.

What it is: CVE-2026-93264 is a vulnerability in Linux, published on 24 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-2026-93264 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-2026-93264/ (Markdown: https://insights.sbomify.com/CVE-2026-93264/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93264
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93264
- OSV: https://osv.dev/vulnerability/CVE-2026-93264

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93264/
Summaries are generated and may contain mistakes; the official description above is the record.