# CVE-2026-80864: RDMA/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp

> A local unprivileged user can trigger a use-after-free in the Linux kernel RDMA responder, causing a 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:** 4 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-99519, BELL-CVE-2026-80864, DEBIAN-CVE-2026-80864, GHSA-6j94-p35f-gvmj, UBUNTU-CVE-2026-80864

## What is CVE-2026-80864?

CVE-2026-80864 is an use after free vulnerability in Linux, published on 4 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/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp

rxe_qp_from_attr() handles IB_QP_MAX_DEST_RD_ATOMIC outside the
IB_QP_STATE path, so it holds no state_lock and runs while the responder
task rxe_receiver() (recv_task on rxe_wq) is live. A modify_qp() setting
only that attribute calls free_rd_atomic_resources() then
alloc_rd_atomic_resources(), swapping qp->resp.resources[] while
rxe_prepare_res()/find_resource() walk it; free_rd_atomic_resources()
also leaves the cached pointer qp->resp.res dangling. A local
unprivileged user can race the free/realloc into a use-after-free in
rxe_receiver() (local DoS).

Drain recv_task around the swap with rxe_disable_task()/rxe_enable_task(),
as rxe_qp_reset() already does when tearing this array down, re-enabling
only after alloc_rd_atomic_resources() succeeds so the responder never
resumes against a NULL qp->resp.resources on the ENOMEM path. Also clear
qp->resp.res in free_rd_atomic_resources(), like the rxe_resp.c
completion paths.

Reproduced under KASAN; the slab-use-after-free in rxe_receiver() is gone.

## Which versions are affected by CVE-2026-80864?


## How do I fix CVE-2026-80864?

Apply the vendor's patch.

## Is CVE-2026-80864 being exploited?

There is no known exploitation of CVE-2026-80864 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80864 and fix it if it is affected.

What it is: CVE-2026-80864 is an use after free vulnerability in Linux, published on 4 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-2026-80864 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-2026-80864/ (Markdown: https://insights.sbomify.com/CVE-2026-80864/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80864
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80864
- OSV: https://osv.dev/vulnerability/CVE-2026-80864

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80864/
Summaries are generated and may contain mistakes; the official description above is the record.