# CVE-2026-90435: RDMA/mlx5: Fix integer overflow of user QP buffer size

> A signed integer overflow in the Linux kernel RDMA driver allows attackers to map undersized buffers, potentially leading to memory corruption and privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-102194, BELL-CVE-2026-90435, DEBIAN-CVE-2026-90435, GHSA-4ff5-3w52-wwv7, UBUNTU-CVE-2026-90435

## What is CVE-2026-90435?

CVE-2026-90435 is a high-severity vulnerability in Linux, published on 17 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/mlx5: Fix integer overflow of user QP buffer size

set_user_buf_size() computes the QP buffer size by left-shifting the
user-supplied rq.wqe_cnt and rq.wqe_shift values as signed integers.
A sufficiently large rq.wqe_cnt causes signed integer overflow, which
is undefined behavior, and yields a small or negative buf_size, causing
ib_umem_get() to map a buffer smaller than the hardware will actually
write into.

Replace the shifts and addition with check_shl_overflow() and
check_add_overflow(), rejecting invalid user inputs.

Moreover, guard the identical shift computing qp->sq.offset in
_create_user_qp() before set_user_buf_size() is reached.

## Which versions are affected by CVE-2026-90435?


## How do I fix CVE-2026-90435?

Apply the vendor's patch.

## Is CVE-2026-90435 being exploited?

There is no known exploitation of CVE-2026-90435 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90435 and fix it if it is affected.

What it is: CVE-2026-90435 is a high-severity vulnerability in Linux, published on 17 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-2026-90435 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-2026-90435/ (Markdown: https://insights.sbomify.com/CVE-2026-90435/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90435
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90435
- OSV: https://osv.dev/vulnerability/CVE-2026-90435

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90435/
Summaries are generated and may contain mistakes; the official description above is the record.